EP2807117A1 - Precipitated-silica production method - Google Patents

Precipitated-silica production method

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Publication number
EP2807117A1
EP2807117A1 EP13701979.0A EP13701979A EP2807117A1 EP 2807117 A1 EP2807117 A1 EP 2807117A1 EP 13701979 A EP13701979 A EP 13701979A EP 2807117 A1 EP2807117 A1 EP 2807117A1
Authority
EP
European Patent Office
Prior art keywords
acid
concentration
weight
silicate
reaction medium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP13701979.0A
Other languages
German (de)
French (fr)
Other versions
EP2807117B1 (en
Inventor
Emmanuelle Allain
Sylvaine Neveu
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rhodia Operations SAS
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Rhodia Operations SAS
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Filing date
Publication date
Application filed by Rhodia Operations SAS filed Critical Rhodia Operations SAS
Publication of EP2807117A1 publication Critical patent/EP2807117A1/en
Application granted granted Critical
Publication of EP2807117B1 publication Critical patent/EP2807117B1/en
Active legal-status Critical Current
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/126—Preparation of silica of undetermined type
    • C01B33/128—Preparation of silica of undetermined type by acidic treatment of aqueous silicate solutions
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
    • C01B33/187—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates
    • C01B33/193—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates of aqueous solutions of silicates

Definitions

  • the present invention relates to a new process for the preparation of precipitated silica.
  • precipitated silicas as a catalyst support, as an absorbent of active substances (in particular liquid carriers, for example used in foodstuffs, such as vitamins (vitamin E in particular), choline chloride), as a viscosifying, texturizing or anti-caking agent, as an element for battery separators, as an additive for toothpaste, for paper.
  • active substances in particular liquid carriers, for example used in foodstuffs, such as vitamins (vitamin E in particular), choline chloride
  • a viscosifying, texturizing or anti-caking agent as an element for battery separators, as an additive for toothpaste, for paper.
  • precipitated silicas as reinforcing filler in silicone matrices (for example for coating electrical cables) or in compositions based on polymer (s), natural or synthetic, in particular elastomer (s), especially diene, for example for shoe soles, floor coverings, gas barriers, fire-retardant materials and also technical parts such as ropeway rollers, appliance seals, liquid or gas line joints, brake system seals, ducts, cables and transmission belts.
  • the main object of the present invention is to provide a new process for the preparation of precipitated silica, which is an alternative to known processes for the preparation of precipitated silica.
  • one of the aims of the present invention is to provide a process having improved productivity, in particular at the level of the precipitation reaction, in particular with respect to the methods of the state of the art implementing as a acid, a dilute acid, which makes it possible to obtain precipitated silicas having physicochemical characteristics and properties comparable to those of the precipitated silicas obtained by these preparative methods of the state of the art.
  • Another object of the invention preferably consists, at the same time, in reducing the quantity of energy consumed and / or the quantity of water used in the preparation of precipitated silica, especially with respect to the methods of the state of the art using as acid a dilute acid.
  • the object of the invention is a new process for the preparation of precipitated silica, comprising the reaction of a silicate with at least one acid, whereby a suspension of silica is obtained, followed by the separation and drying of this silica. suspension, in which the reaction of the silicate with the acid is carried out according to the following successive stages: (i) an initial aqueous base stock comprising alkali metal silicate M is formed, the silicate concentration (expressed in S102) of said foot less than 20 g / l, preferably at most 15 g / l,
  • alkali metal silicate M and acid are added to the reaction medium in such a way that the ratio of the amount of silicate added (expressed as SiO 2) / amount of silicate present in the initial base stock ( expressed in S102) is greater than 4 and not more than 100, preferably between 12 and 100, in particular between 12 and 50,
  • step (v) the reaction medium obtained at the end of step (iv) is brought into contact (mixture) (thus having a pH of between 2.5 and 5.3, preferably between 2.8 and 5.2 ) with acid and silicate, such that the pH of the reaction medium is maintained between 2.5 and 5.3, preferably between 2.8 and 5.2, in which process:
  • step (iii) in at least a part of step (iii) (i.e. in at least some or all of step (iii))
  • the acid used is a concentrated acid, preferably selected from the group consisting of sulfuric acid having a concentration of at least 80% by weight, in particular at least 90% by weight, acetic acid or formic acid having a concentration of at least 90% by weight, the nitric acid having a concentration of at least 60% by weight, the phosphoric acid having a concentration of at least 75% by weight, the acid hydrochloric acid having a concentration of at least 30% by mass.
  • said concentrated acid is concentrated sulfuric acid, that is to say sulfuric acid having a concentration of at least 80% by weight, preferably at least 90% by weight.
  • step (vi) sulfuric acid having a concentration of at least 1400 g / l, in particular at least 1650 g / l. It is possible, in a subsequent step (vi), to add, in the reaction medium obtained at the end of step (v), an alkaline agent, preferably a silicate, until it reaches pH value of the reaction medium of between 4.7 and 6.3, preferably between 5.0 and 5.8, for example between 5.0 and 5.4.
  • an alkaline agent preferably a silicate
  • the acid used in step (v) is a concentrated acid as defined above.
  • the acid used in steps (ii), (iii) and (iv) can then be, for example, a dilute acid, advantageously dilute sulfuric acid, that is to say having a concentration much lower than 80% by weight, in this case a concentration of less than 20% by weight (and in general of at least 4% by weight), in particular less than 14% by weight, especially not more than 10% by weight, for example between 5 and 10% by weight.
  • the invention is a new process for the preparation of precipitated silica comprising the reaction of a silicate with at least one acid, whereby a suspension of silica is obtained. , then separating and drying this suspension, in which the reaction of the silicate with the acid is carried out according to the following successive steps:
  • alkali metal silicate M and acid are added to the reaction medium in such a way that the ratio of the amount of silicate added (expressed as SiO 2) / amount of silicate present in the initial base stock ( expressed in S102) is greater than 4 and not more than 100, preferably between 12 and 100, in particular between 12 and 50,
  • step (v) the reaction medium obtained at the end of step (iv) is brought into contact (mixture) (thus having a pH of between 2.5 and 5.3, preferably between 2.8 and 5.2 ) with acid and silicate, so that the pH of the reaction medium is maintained between 2.5 and 5.3, preferably between 2.8 and 5.2, in which process in at least a portion of step (iii) (i.e., in at least a portion or all of step (iii)), the acid used is a concentrated acid, preferably selected from the group consisting of sulfuric acid having a concentration of at least 80% by weight, in particular at least 90% by weight, the acetic acid or formic acid having a concentration of at least 90% by weight, nitric acid having a concentration of at least 60% by weight, the phosphoric acid having a concentration of at least 75% by weight, the hydrochloric acid having a concentration of at least 30% by weight.
  • the acid used is a concentrated acid, preferably selected from the group consisting of sulfuric acid having
  • said concentrated acid is concentrated sulfuric acid, that is to say sulfuric acid having a concentration of at least 80% by weight, preferably at least 90% by weight.
  • the acid used in a part of step (iii), preferably in step (iii) (this is in all of step (iii)), is a concentrated acid, preferably selected from the group consisting of sulfuric acid having a concentration of at least 80% by weight, in particular at least 90% by weight.
  • acetic acid or formic acid having a concentration of at least 90% by weight
  • the nitric acid having a concentration of at least 60% by weight
  • the phosphoric acid having a concentration of at least 75% by mass
  • hydrochloric acid having a concentration of at least 30% by mass.
  • said concentrated acid is concentrated sulfuric acid, that is to say sulfuric acid having a concentration of at least 80% by weight (and generally at most 98% by weight). ), preferably at least 90% by weight; in particular, its concentration is between 90 and 98% by weight, for example between 91 and 97% by weight.
  • the concentrated acid as defined above is used only in step (iii).
  • the acid used in steps (ii), (iv) and (v) can then be for example a dilute acid, advantageously dilute sulfuric acid, that is to say having a concentration much lower than 80% by weight, in this case a concentration of less than 20% by weight (and in general of at least 4% by weight), in particular less than 14% by weight, especially not more than 10% by weight, for example between 5 and 10% by weight.
  • a dilute acid advantageously dilute sulfuric acid, that is to say having a concentration much lower than 80% by weight, in this case a concentration of less than 20% by weight (and in general of at least 4% by weight), in particular less than 14% by weight, especially not more than 10% by weight, for example between 5 and 10% by weight.
  • the acid used in step (iv) is also a concentrated acid as mentioned above.
  • the acid used in steps (iv) and (v) is also a concentrated acid as mentioned above.
  • the acid used in the whole of step (ii) may then be for example a diluted acid as described above
  • the acid used in the whole of step (ii) may also be a concentrated acid as mentioned above, advantageously acid concentrated sulfuric acid, that is to say having a concentration of at least 80% by weight, preferably at least 90% by weight, in particular between 90 and 98% by weight.
  • acid concentrated sulfuric acid that is to say having a concentration of at least 80% by weight, preferably at least 90% by weight, in particular between 90 and 98% by weight.
  • water in the initial stock especially before step (ii) or during step (ii).
  • the choice of the acid, the optional alkaline agent and the alkali metal silicate M is in a manner well known per se.
  • the acid (s) is generally an organic acid such as acetic acid, formic acid or carbonic acid or, preferably, a mineral acid such as sulfuric nitric acid, phosphoric acid or hydrochloric acid.
  • concentrated acetic acid or concentrated formic acid is used as the concentrated acid, then their concentration is at least 90% by weight.
  • concentrated nitric acid is used as concentrated acid, then its concentration is at least 60% by weight.
  • concentrated concentrated phosphoric acid If concentrated concentrated phosphoric acid is used, then its concentration is at least 75% by weight.
  • concentrated hydrochloric acid is used as concentrated acid, then its concentration is at least 30% by weight.
  • the acid (s) used is sulfuric acid (s), the concentrated sulfuric acid then used having a concentration as already mentioned in the above discussion.
  • silicate any common form of silicates such as metasilicates, disilicates and advantageously an alkali metal silicate M in which M is sodium or potassium.
  • the silicate may have a concentration (expressed as SiO 2) of between 2 and 330 g / l, for example between 3 and 300 g / l, in particular between 4 and 260 g / l.
  • the silicate used is sodium silicate.
  • sodium silicate In the case where sodium silicate is used, it generally has a weight ratio SiO 2 / Na 2 O of between 2.5 and 4, for example between 3.2 and 3.8.
  • the alkaline agent employed in the optional step (vi) may be, for example, a solution of sodium hydroxide, potassium hydroxide or ammonia.
  • this alkaline agent is silicate, in particular silicate as used in the preceding steps.
  • the reaction of the silicate with the acid is in a very specific manner according to the following steps.
  • First (step (i)) is formed an aqueous stock which comprises silicate.
  • the silicate concentration (expressed in S102) of this initial base stock is less than 20 g / l.
  • This concentration is preferably at most 15 g / l, in particular at most 1 1 g / l, for example at most 8 g / l.
  • the vessel stock formed in step (i) may optionally comprise an electrolyte. Nevertheless, preferably, no electrolyte is added during the preparation process, in particular in step (i).
  • electrolyte is here understood in its normal acceptation, that is to say that it signifies any ionic or molecular substance which, when in solution, decomposes or dissociates to form ions or charged particles.
  • electrolyte mention may be made of a salt of the group of alkali and alkaline earth metal salts, in particular the salt of the starting silicate metal and of the acid, for example sodium chloride in the case of the reaction of a silicate of sodium with hydrochloric acid or, preferably, sodium sulfate in the case of the reaction of a sodium silicate with sulfuric acid.
  • the second step (step (ii)) is to add acid in the initial stock.
  • step (Ni) acid is added to said initial base stock until at least 50%, in particular 50% to 99%, of the quantity of M 2 O present in said initial base stock. neutralized.
  • step (Ni) a simultaneous addition (step (Ni)) of acid and an amount of alkali metal silicate M such as the consolidation rate are then carried out.
  • the ratio amount of silicate added (expressed as SiO 2 ) / amount of silicate present in the initial stock (expressed in SiO 2 ) is greater than 4 and at most 100.
  • this simultaneous addition of acid and a quantity of alkali metal silicate M is carried out so that the consolidation ratio is preferably between 12 and 100, in particular between 12 and 50, especially between 13 and 40.
  • this simultaneous addition of acid and a quantity of alkali metal silicate M is carried out in such a way that the consolidation ratio is rather greater than 4 and less than 12, particular between 5 and 1 1, 5, especially between 7.5 and 1 1.
  • This variant is, in general, implemented when the silicate concentration in the initial stock is at least 8 g / l, in particular between 10 and 15 g / l, for example between 11 and 15 g. / L.
  • the amount of added acid is such that 80 to 99%, for example 85 to 97%, of the amount of M 2 O added are neutralized.
  • step (iii) it is possible to proceed to the simultaneous addition of acid and silicate at a first pH level of the reaction medium, ⁇ - ⁇ , then at a second pH level of the reaction medium, pH 2 , such as 7 ⁇ pH 2 ⁇ pHi ⁇ 9.
  • a step (iv) the addition of the silicate is stopped while continuing the addition of acid in the reaction medium so as to obtain a pH value of the reaction medium of between 2.5 and 5.3 (for example between 3.0 and 5.3), preferably between 2.8 and 5.2 (for example between 4.0 and 5.2), in particular between 3.5 and 5.1 (or even between 3, 5 and 5.0).
  • this curing can for example last from 2 to 45 minutes, in particular from 5 to 20 minutes, and preferably does not include any addition of acid or addition of silicate.
  • step (v) the reaction medium obtained at the end of stage (iv), said reaction medium thus having a pH of between 2.5 and 5.3, preferably between 2.8 and 5.2, for example between 3, 5 and 5.1 (or between 3.5 and 5.0),
  • Said pH of the reaction medium may vary within the range 2.5-5.3, preferably in the range 2.8-5.2, for example in the range 3.5-5.1 (even 3 , 5-5,0), or, preferably, remain (substantially) constant within these ranges.
  • step (v) the contacting of the reaction medium resulting from step (iv) with the acid and the silicate (for example the alkali metal silicate M) is carried out by adding acid. and silicate said reaction medium.
  • the silicate for example the alkali metal silicate M
  • step (v) the acid and then the silicate are added to said reaction medium.
  • step (v) the acid and the silicate (for example the alkali metal silicate M) are added simultaneously to said reaction medium; preferably, this simultaneous addition is carried out with regulation of the pH of the reaction medium obtained during this addition to a value (substantially) constant within the aforementioned ranges.
  • the silicate for example the alkali metal silicate M
  • Step (v) is generally carried out with stirring.
  • step (vi) of the process according to the invention consists of an addition, in the reaction medium obtained at the end of step (v), of an alkaline agent, preferably of silicate (in particular of silicate of alkali metal M), until a pH value of the reaction medium is between 4.7 and 6.3, preferably between 5.0 and 5.8, for example between 5.0 and 5.4. .
  • an alkaline agent preferably of silicate (in particular of silicate of alkali metal M)
  • This step (vi) is usually carried out with stirring.
  • step (i) to (v), or (vi) if necessary) is carried out with stirring.
  • All steps (i) to (v), or (vi) where appropriate are usually carried out between 75 and 97 ° C, preferably between 80 and 96 ° C. According to a variant of the process of the invention, all the steps are carried out at a constant temperature.
  • the end-of-reaction temperature is higher than the Reaction start temperature: thus, the temperature is maintained at the start of the reaction (for example during steps (i) and (ii)) preferably between 75 and 90 ° C, then the temperature is increased, preferably until at a value between 90 and 97 ° C, the value at which it is maintained (for example during steps (iii) to (vi)) until the end of the reaction.
  • step (v) it may be advantageous to proceed at the end of step (v) or of the optional step (vi) to a maturation of the reaction medium obtained, in particular at the pH obtained at the end of this step (v) ( or step (vi)), and in general with stirring.
  • This curing can for example last from 2 to 30 minutes, in particular from 3 to 20 minutes and can be carried out between 75 and 97 ° C., preferably between 80 and 96 ° C., in particular at the temperature at which the reaction was carried out.
  • step (v) (or step (vi) It preferably does not include any addition of acid or addition of silicate.
  • step (v) may be carried out in a fast mixer or in a turbulent flow zone, which may allow better control of the characteristics of the precipitated silicas obtained.
  • step (v) the acid then the silicate (for example metal silicate) is added to the reaction mixture obtained at the end of step (iv). alkali M), then the contacting of said silicate with the medium resulting from the addition of the acid to the reaction medium obtained at the end of step (iv) can be carried out in a fast mixer or in a zone d turbulent flow.
  • the silicate for example metal silicate
  • step (v) the acid and the silicate (for example alkali metal silicate M) are added simultaneously to the reaction medium obtained at the end of step (iv). , then bringing said acid and said silicate into contact with said reaction medium can be carried out in a fast mixer or in a turbulent flow zone.
  • the acid and the silicate for example alkali metal silicate M
  • the reaction medium obtained in the fast mixer or in a turbulent flow zone feeds a reactor, preferably subjected to agitation, reactor in which the optional step (vi) is implemented.
  • step (v) it is possible to use a fast mixer chosen from symmetrical T or Y mixers, asymmetrical T or Y mixers, tangential jet mixers and mixers. Hartridge-Roughton, vortex mixers, rotor-stator mixers.
  • T or symmetrical Y are usually made of two opposite tubes (T-tubes) or forming an angle less than 180 ° (Y-tubes), of the same diameter, discharging into a central tube whose diameter is identical to or greater than that of the two previous tubes. They are called "symmetrical" because the two reagent injection tubes have the same diameter and the same angle with respect to the central tube, the device being characterized by an axis of symmetry.
  • the central tube has a diameter about twice as large as the diameter of the opposed tubes; similarly the fluid velocity in the central tube is preferably half that in the opposite tubes.
  • an asymmetrical T-shaped or Y-shaped mixer or tube
  • a symmetrical T-shaped or Y-shaped mixer or tube
  • one of the fluids is injected into the central tube by means of a smaller diameter side tube.
  • the latter forms with the central tube an angle of 90 ° in general (T-tube); this angle may be different from 90 ° (Y-tube), giving co-current systems (for example 45 ° angle) or counter-current (for example 135 ° angle) relative to the other current.
  • a fast mixer As a fast mixer, a tangential jet mixer, a Hartridge-Roughton mixer or a vortex mixer (or precipitator) are preferably used, which are derived from symmetrical T-shaped devices.
  • step (v) it is possible to use a tangential jet fast mixer, Hartridge-Roughton or vortex, comprising a chamber having (a) at least two tangential admissions through which enter separately (but at the same time ) on the one hand, the silicate, and on the other hand, the medium resulting from the addition of acid to the reaction medium resulting from step (iv), namely, on the one hand, silicate and the acid, and on the other hand, the reaction medium resulting from step (iv), and (b) an axial outlet through which the reaction medium obtained in this step (v) leaves, preferably to a reactor (tank) arranged in series after said mixer.
  • the two tangential admissions are of preferably located symmetrically and oppositely to the central axis of said chamber.
  • the mixer chamber with tangential jets, Hartridge-Roughton or vortex optionally used generally has a circular section and is preferably of cylindrical shape.
  • Each tangential inlet tube may have an internal diameter d of 0.5 to 80 mm.
  • This internal diameter d may be between 0.5 and 10 mm, in particular between 1 and 9 mm, for example between 2 and 7 mm. However, especially on an industrial scale, it is preferably between 10 and 80 mm, in particular between 20 and 60 mm, for example between 30 and 50 mm.
  • the internal diameter of the chamber of the tangential jet mixer, Hartridge-Roughton or vortex optionally used may be between 3d and 6d, in particular between 3d and 5d, for example equal to 4d; the internal diameter of the axial outlet tube may be between 1 d and 3d, in particular between 1.5d and 2.5d, for example equal to 2d.
  • the flow rates of the silicate and the acid are for example determined so that at the confluence point the two reactant streams come into contact with each other in a sufficiently turbulent flow zone.
  • step (v) a silica slurry is obtained, which is optionally followed by maturing. separated (liquid-solid separation).
  • the separation used in the preparation process according to the invention usually comprises a filtration, followed by washing if necessary.
  • the filtration is carried out by any suitable method, for example by means of a filter press, a belt filter, a vacuum filter.
  • the silica suspension thus recovered (filter cake) is then dried.
  • This drying can be done by any means known per se.
  • the drying is done by atomization.
  • any suitable type of atomizer may be used, such as a turbine, nozzle, liquid pressure or two-fluid atomizer.
  • a turbine nozzle
  • liquid pressure two-fluid atomizer.
  • the filter cake is not always under conditions allowing atomization, in particular because of its viscosity. high.
  • the cake is then subjected to a disintegration operation.
  • This operation can be performed mechanically, by passing the cake in a colloid mill or ball.
  • the disintegration is generally carried out in the presence of water and / or in the presence of an aluminum compound, in particular sodium aluminate and, optionally, in the presence of an acid as described above (in the latter case the aluminum compound and the acid are usually added simultaneously).
  • the disintegration operation makes it possible in particular to lower the viscosity of the suspension to be dried later.
  • the silica that can then be obtained is usually in the form of substantially spherical balls.
  • the silica that is then likely to be obtained is generally in the form of a powder.
  • the silica that may then be obtained may be in the form of a powder.
  • the dried product in particular by a turbine atomizer or milled as indicated above may optionally be subjected to an agglomeration step, which consists, for example, of a direct compression, a wet-path granulation (that is, with the use of a binder such as water, silica suspension, etc.), extrusion or, preferably, dry compaction.
  • an agglomeration step which consists, for example, of a direct compression, a wet-path granulation (that is, with the use of a binder such as water, silica suspension, etc.), extrusion or, preferably, dry compaction.
  • the silica that can then be obtained by this agglomeration step is generally in the form of granules.
  • the powders, as well as the silica beads, obtained by the process according to the invention thus offer the advantage, among others, of having a simple, effective and economical way of accessing granules, in particular by conventional setting operations. shaped, such as for example granulation or compaction.
  • the precipitated silicas prepared by the process according to the invention are generally in at least one of the following forms: substantially spherical beads, powder, granules.
  • the process according to the invention makes it possible to obtain silicas formed from aggregates of large primary particles of silica, on the surface of which there are small primary particles of silica.
  • the implementation of the preparation method according to the invention makes it possible in particular to obtain during said process (at the end of step (v) or of the optional step (vi)) a more concentrated suspension of precipitated silica than that obtained by an identical process using only dilute acid, and therefore a productivity gain in precipitated silica (which can reach for example at least 10 to 40 %), in particular to the precipitation reaction (that is to say at the end of step (v) or of the possible step (vi)), while surprisingly accompanying the obtaining precipitated silicas having, preferably, a particular morphology, particle size and porosity.
  • the precipitated silicas obtained by the process according to the invention preferably have good dispersibility in the polymers and give them a compromise of satisfactory properties, for example in terms of their mechanical, dynamic and rheological, comparable to those precipitated silicas obtained by an identical process using only diluted acid.
  • the process according to the invention makes it possible, compared to an identical process employing only dilute acid, a gain ( reach for example at least 15 to 60%) on the energy consumption (in the form of live steam for example), in particular the precipitation reaction (that is to say at the end of the step ( v) or possible step (vi)), due to a decrease in the quantities of water involved and the exothermic nature of the use of concentrated acid.
  • the use of concentrated acid makes it possible to restrict (for example by at least 15%) the quantity of water required for the reaction, in particular because of the reduction in the quantity of water used for the preparation of acid.
  • the precipitated silica prepared by the process according to the invention can be used in various applications. It can be used, for example, as a catalyst support, as an absorbent of active substances (in particular a carrier for liquids, especially used in foodstuffs, such as vitamins (vitamin E), choline chloride), in polymer compositions. (s), in particular elastomer (s), silicone (s), as viscosity agent, texturizing or anti-caking, as an element for battery separators, additive for toothpaste, for concrete, for paper.
  • active substances in particular a carrier for liquids, especially used in foodstuffs, such as vitamins (vitamin E), choline chloride
  • s in particular elastomer (s), silicone (s), as viscosity agent, texturizing or anti-caking, as an element for battery separators, additive for toothpaste, for concrete, for paper.
  • It can be used for reinforcing polymers, natural or synthetic.
  • the polymer compositions in which the precipitated silicas prepared by the process according to the invention can be used, in particular as reinforcing filler, are generally based on one or more polymers or copolymers, in particular a or more elastomers, especially thermoplastic elastomers, preferably having at least a glass transition temperature of between -150 and +300 ° C, for example between -150 and +20 ° C.
  • diene polymers in particular diene elastomers.
  • finished articles based on the polymer compositions described above, such as shoe soles, tires, floor coverings, gas barriers, fireproofing materials and the like. also technical parts such as ropeway rollers, appliance joints, liquid or gas line joints, brake system joints, hoses, ducts (especially cable ducts) , cables, motor mounts, conveyor belts and transmission belts.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Silicon Compounds (AREA)

Abstract

The invention relates to a method for producing precipitated silicas, comprising: (i) forming a starter having an alkali metal silicate M concentration of less than 20 g/L; (ii) adding acid thereto until at least 50% of the quantity of M2O is neutralised; (iii) adding silicate and acid simultaneously, such that the consolidation rate is greater than 4 and at most 100; (iv) adding acid until the pH measures between 2.5 and 5.3; (v) bringing the reaction medium into contact with the acid and the silicate, such that the pH measures between 2.5 and 5.3. According to the invention, the acid used in at least one of the steps is a concentrated acid, preferably selected from the group containing sulphuric acid having a concentration of at least 80 wt.-%, in particular at least 90 wt.-%, acetic acid or formic acid having a concentration of at least 90 wt.-%, nitric acid having a concentration of at least 60 wt.-%, phosphoric acid having a concentration of at least 75 wt.-%, hydrochloric acid having a concentration of at least 30 wt.-%.

Description

PROCÉDÉ DE PRÉPARATION DE SILICES PRÉCIPITÉES  PROCESS FOR THE PREPARATION OF PRECIPITATED SILICA
La présente invention concerne un nouveau procédé de préparation de silice précipitée. The present invention relates to a new process for the preparation of precipitated silica.
Il est connu d'employer des silices précipitées comme support de catalyseur, comme absorbant de matières actives (en particulier supports de liquides, par exemple utilisés dans l'alimentation, tels que les vitamines (vitamine E notamment), le chlorure de choline), comme agent viscosant, texturant ou anti- mottant, comme élément pour séparateurs de batteries, comme additif pour dentifrice, pour papier.  It is known to employ precipitated silicas as a catalyst support, as an absorbent of active substances (in particular liquid carriers, for example used in foodstuffs, such as vitamins (vitamin E in particular), choline chloride), as a viscosifying, texturizing or anti-caking agent, as an element for battery separators, as an additive for toothpaste, for paper.
On peut également employer des silices précipitées comme charge renforçante dans des matrices silicones (par exemple pour l'enrobage des câbles électriques) ou dans des compositions à base de polymère(s), naturel(s) ou synthétique(s), en particulier d'élastomère(s), notamment diéniques, par exemple pour les semelles de chaussures, les revêtements de sols, les barrières aux gaz, les matériaux ignifugeants et également les pièces techniques telles que les galets de téléphériques, les joints d'appareils électroménagers, les joints de conduites de liquides ou de gaz, les joints de système de freinage, les gaines, les câbles et les courroies de transmissions.  It is also possible to use precipitated silicas as reinforcing filler in silicone matrices (for example for coating electrical cables) or in compositions based on polymer (s), natural or synthetic, in particular elastomer (s), especially diene, for example for shoe soles, floor coverings, gas barriers, fire-retardant materials and also technical parts such as ropeway rollers, appliance seals, liquid or gas line joints, brake system seals, ducts, cables and transmission belts.
Il est ainsi connu de préparer, en mettant en œuvre une réaction de précipitation entre un silicate et un acide dilué, des silices précipitées, utilisables comme charge renforçante pour les compositions de polymères. It is thus known to prepare, by carrying out a precipitation reaction between a silicate and a dilute acid, precipitated silicas, which can be used as reinforcing filler for the polymer compositions.
Le but principal de la présente invention est de proposer un nouveau procédé de préparation de silice précipitée, qui constitue une alternative aux procédés connus de préparation de silice précipitée. The main object of the present invention is to provide a new process for the preparation of precipitated silica, which is an alternative to known processes for the preparation of precipitated silica.
Plus préférentiellement, l'un des buts de la présente invention consiste à fournir un procédé ayant une productivité améliorée, en particulier au niveau de la réaction de précipitation, notamment par rapport aux procédés de l'état de la technique mettant en œuvre à titre d'acide un acide dilué, et qui permet d'obtenir des silices précipitées ayant des caractéristiques physicochimiques et des propriétés comparables à celles des silices précipitées obtenues par ces procédés de préparation de l'état de la technique.  More preferably, one of the aims of the present invention is to provide a process having improved productivity, in particular at the level of the precipitation reaction, in particular with respect to the methods of the state of the art implementing as a acid, a dilute acid, which makes it possible to obtain precipitated silicas having physicochemical characteristics and properties comparable to those of the precipitated silicas obtained by these preparative methods of the state of the art.
Un autre but de l'invention consiste préférentiellement, dans le même temps, à réduire la quantité d'énergie consommée et/ou la quantité d'eau employée lors de la préparation de silice précipitée, notamment par rapport aux procédés de l'état de la technique mettant en œuvre à titre d'acide un acide dilué. Another object of the invention preferably consists, at the same time, in reducing the quantity of energy consumed and / or the quantity of water used in the preparation of precipitated silica, especially with respect to the methods of the state of the art using as acid a dilute acid.
Ainsi, l'objet de l'invention est un nouveau procédé de préparation de silice précipitée comprenant la réaction d'un silicate avec au moins un acide ce par quoi l'on obtient une suspension de silice, puis la séparation et le séchage de cette suspension, dans lequel la réaction du silicate avec l'acide est réalisée selon les étapes successives suivantes : (i) on forme un pied de cuve aqueux initial comportant du silicate de métal alcalin M, la concentration en silicate (exprimée en S1O2) dudit pied de cuve étant inférieure à 20 g/L, de préférence d'au plus 15 g/L, Thus, the object of the invention is a new process for the preparation of precipitated silica, comprising the reaction of a silicate with at least one acid, whereby a suspension of silica is obtained, followed by the separation and drying of this silica. suspension, in which the reaction of the silicate with the acid is carried out according to the following successive stages: (i) an initial aqueous base stock comprising alkali metal silicate M is formed, the silicate concentration (expressed in S102) of said foot less than 20 g / l, preferably at most 15 g / l,
(ii) on ajoute de l'acide audit pied de cuve initial, jusqu'à ce qu'au moins 50 % de la quantité de M2O présente dans le dit pied de cuve initial soient neutralisés, (ii) adding acid to said initial stock, until at least 50% of the amount of M 2 O present in said initial stock is neutralized,
(iii) on ajoute au milieu réactionnel, simultanément, du silicate de métal alcalin M et de l'acide, de telle manière que le rapport quantité de silicate ajoutée (exprimée en S1O2) / quantité de silicate présente dans le pied de cuve initial (exprimée en S1O2) soit supérieur à 4 et d'au plus 100, de préférence soit compris entre 12 et 100, en particulier entre 12 et 50, (iii) at the same time, alkali metal silicate M and acid are added to the reaction medium in such a way that the ratio of the amount of silicate added (expressed as SiO 2) / amount of silicate present in the initial base stock ( expressed in S102) is greater than 4 and not more than 100, preferably between 12 and 100, in particular between 12 and 50,
(iv) on arrête l'addition du silicate tout en continuant l'addition de l'acide dans le milieu réactionnel jusqu'à l'obtention d'une valeur du pH du milieu réactionnel comprise entre 2,5 et 5,3, de préférence entre 2,8 et 5,2, (iv) stopping the addition of the silicate while continuing the addition of the acid in the reaction medium until a pH value of the reaction medium of between 2.5 and 5.3 is obtained; preferably between 2.8 and 5.2,
(v) on met en contact (mélange) le milieu réactionnel obtenu à l'issue de l'étape (iv) (présentant donc un pH compris entre 2,5 et 5,3, de préférence entre 2,8 et 5,2) avec de l'acide et du silicate, de telle manière que le pH du milieu réactionnel soit maintenu entre 2,5 et 5,3, de préférence entre 2,8 et 5,2, procédé dans lequel : (v) the reaction medium obtained at the end of step (iv) is brought into contact (mixture) (thus having a pH of between 2.5 and 5.3, preferably between 2.8 and 5.2 ) with acid and silicate, such that the pH of the reaction medium is maintained between 2.5 and 5.3, preferably between 2.8 and 5.2, in which process:
- dans au moins une partie de l'étape (iii) (c'est-à-dire dans, au minimum, une partie ou la totalité de l'étape (iii))  in at least a part of step (iii) (i.e. in at least some or all of step (iii))
et/ou and or
- dans au moins l'étape (v) l'acide utilisé est un acide concentré, de préférence choisi dans le groupe formé par l'acide sulfurique présentant une concentration d'au moins 80 % en masse, en particulier d'au moins 90 % en masse, l'acide acétique ou l'acide formique présentant une concentration d'au moins 90 % en masse, l'acide nitrique présentant une concentration d'au moins 60 % en masse, l'acide phosphorique présentant une concentration d'au moins 75 % en masse, l'acide chlorhydrique présentant une concentration d'au moins 30 % en masse. in at least step (v) the acid used is a concentrated acid, preferably selected from the group consisting of sulfuric acid having a concentration of at least 80% by weight, in particular at least 90% by weight, acetic acid or formic acid having a concentration of at least 90% by weight, the nitric acid having a concentration of at least 60% by weight, the phosphoric acid having a concentration of at least 75% by weight, the acid hydrochloric acid having a concentration of at least 30% by mass.
De manière avantageuse, ledit acide concentré est de l'acide sulfurique concentré, c'est-à-dire de l'acide sulfurique présentant une concentration d'au moins 80 % en masse, de préférence d'au moins 90 % en masse. Advantageously, said concentrated acid is concentrated sulfuric acid, that is to say sulfuric acid having a concentration of at least 80% by weight, preferably at least 90% by weight.
On peut ainsi utiliser, comme acide concentré, de l'acide sulfurique ayant une concentration d'au moins 1400 g/L, en particulier d'au moins 1650 g/L. II est possible, dans une éventuelle étape (vi) ultérieure, d'ajouter, dans le milieu réactionnel obtenu à l'issue de l'étape (v), un agent alcalin, de préférence un silicate, et ce jusqu'à atteindre une valeur du pH du milieu réactionnel comprise entre 4,7 et 6,3, de préférence entre 5,0 et 5,8, par exemple entre 5,0 et 5,4.  It is thus possible to use, as concentrated acid, sulfuric acid having a concentration of at least 1400 g / l, in particular at least 1650 g / l. It is possible, in a subsequent step (vi), to add, in the reaction medium obtained at the end of step (v), an alkaline agent, preferably a silicate, until it reaches pH value of the reaction medium of between 4.7 and 6.3, preferably between 5.0 and 5.8, for example between 5.0 and 5.4.
Selon une variante (A) du procédé de l'invention, l'acide utilisé dans l'étape (v) est un acide concentré tel que défini ci-dessus. According to a variant (A) of the process of the invention, the acid used in step (v) is a concentrated acid as defined above.
L'acide utilisé dans les étapes (ii), (iii) et (iv) peut alors être par exemple un acide dilué, de manière avantageuse de l'acide sulfurique dilué, c'est-à-dire présentant une concentration très inférieure à 80 % en masse, en l'occurrence une concentration inférieure à 20 % en masse (et en général d'au moins 4 % en masse), en particulier inférieure à 14 % en masse, notamment d'au plus 10 % en masse, par exemple comprise entre 5 et 10 % en masse. Selon la variante préférée de l'invention (variante (B)), l'invention est un nouveau procédé de préparation de silice précipitée comprenant la réaction d'un silicate avec au moins un acide ce par quoi l'on obtient une suspension de silice, puis la séparation et le séchage de cette suspension, dans lequel la réaction du silicate avec l'acide est réalisée selon les étapes successives suivantes :  The acid used in steps (ii), (iii) and (iv) can then be, for example, a dilute acid, advantageously dilute sulfuric acid, that is to say having a concentration much lower than 80% by weight, in this case a concentration of less than 20% by weight (and in general of at least 4% by weight), in particular less than 14% by weight, especially not more than 10% by weight, for example between 5 and 10% by weight. According to the preferred variant of the invention (variant (B)), the invention is a new process for the preparation of precipitated silica comprising the reaction of a silicate with at least one acid, whereby a suspension of silica is obtained. , then separating and drying this suspension, in which the reaction of the silicate with the acid is carried out according to the following successive steps:
(i) on forme un pied de cuve aqueux initial comportant du silicate de métal alcalin M, la concentration en silicate (exprimée en S1O2) dudit pied de cuve étant inférieure à 20 g/L, de préférence d'au plus 15 g/L, (ii) on ajoute de l'acide audit pied de cuve initial, jusqu'à ce qu'au moins 50 % de la quantité de M2O présente dans le dit pied de cuve initial soient neutralisés, (i) forming an initial aqueous base stock comprising alkali metal silicate M, the silicate concentration (expressed as SiO 2) of said stock base being less than 20 g / l, preferably at most 15 g / l , (ii) adding acid to said initial stock, until at least 50% of the amount of M 2 O present in said initial stock is neutralized,
(iii) on ajoute au milieu réactionnel, simultanément, du silicate de métal alcalin M et de l'acide, de telle manière que le rapport quantité de silicate ajoutée (exprimée en S1O2) / quantité de silicate présente dans le pied de cuve initial (exprimée en S1O2) soit supérieur à 4 et d'au plus 100, de préférence soit compris entre 12 et 100, en particulier entre 12 et 50, (iii) at the same time, alkali metal silicate M and acid are added to the reaction medium in such a way that the ratio of the amount of silicate added (expressed as SiO 2) / amount of silicate present in the initial base stock ( expressed in S102) is greater than 4 and not more than 100, preferably between 12 and 100, in particular between 12 and 50,
(iv) on arrête l'addition du silicate tout en continuant l'addition de l'acide dans le milieu réactionnel jusqu'à l'obtention d'une valeur du pH du milieu réactionnel comprise entre 2,5 et 5,3, de préférence entre 2,8 et 5,2, (iv) stopping the addition of the silicate while continuing the addition of the acid in the reaction medium until a pH value of the reaction medium of between 2.5 and 5.3 is obtained; preferably between 2.8 and 5.2,
(v) on met en contact (mélange) le milieu réactionnel obtenu à l'issue de l'étape (iv) (présentant donc un pH compris entre 2,5 et 5,3, de préférence entre 2,8 et 5,2) avec de l'acide et du silicate, de telle manière que le pH du milieu réactionnel soit maintenu entre 2,5 et 5,3, de préférence entre 2,8 et 5,2, procédé dans lequel dans au moins une partie de l'étape (iii) (c'est-à-dire dans, au minimum, une partie ou la totalité de l'étape (iii)), l'acide utilisé est un acide concentré, de préférence choisi dans le groupe formé par l'acide sulfurique présentant une concentration d'au moins 80 % en masse, en particulier d'au moins 90 % en masse, l'acide acétique ou l'acide formique présentant une concentration d'au moins 90 % en masse, l'acide nitrique présentant une concentration d'au moins 60 % en masse, l'acide phosphorique présentant une concentration d'au moins 75 % en masse, l'acide chlorhydrique présentant une concentration d'au moins 30 % en masse. (v) the reaction medium obtained at the end of step (iv) is brought into contact (mixture) (thus having a pH of between 2.5 and 5.3, preferably between 2.8 and 5.2 ) with acid and silicate, so that the pH of the reaction medium is maintained between 2.5 and 5.3, preferably between 2.8 and 5.2, in which process in at least a portion of step (iii) (i.e., in at least a portion or all of step (iii)), the acid used is a concentrated acid, preferably selected from the group consisting of sulfuric acid having a concentration of at least 80% by weight, in particular at least 90% by weight, the acetic acid or formic acid having a concentration of at least 90% by weight, nitric acid having a concentration of at least 60% by weight, the phosphoric acid having a concentration of at least 75% by weight, the hydrochloric acid having a concentration of at least 30% by weight.
De manière avantageuse, ledit acide concentré est de l'acide sulfurique concentré, c'est-à-dire de l'acide sulfurique présentant une concentration d'au moins 80 % en masse, de préférence d'au moins 90 % en masse. Advantageously, said concentrated acid is concentrated sulfuric acid, that is to say sulfuric acid having a concentration of at least 80% by weight, preferably at least 90% by weight.
On peut ainsi utiliser, comme acide concentré, de l'acide sulfurique ayant une concentration d'au moins 1400 g/L, en particulier d'au moins 1650 g/L. Ainsi, selon l'une des caractéristiques essentielles de la variante (B), prise en combinaison avec un enchaînement d'étapes aux conditions spécifiques, en particulier une certaine concentration en silicate de métal alcalin, ainsi qu'un rapport de quantité de silicate ajoutée (exprimée en S1O2) / quantité de silicate présente dans le pied de cuve initial (exprimée en S1O2) approprié, l'acide utilisé dans une partie de l'étape (iii), préférentiellement dans l'étape (iii) (c'est à daire dans la totalité de l'étape (iii)), est un acide concentré, de préférence choisi dans le groupe formé par l'acide sulfurique présentant une concentration d'au moins 80 % en masse, en particulier d'au moins 90 % en masse, l'acide acétique ou l'acide formique présentant une concentration d'au moins 90 % en masse, l'acide nitrique présentant une concentration d'au moins 60 % en masse, l'acide phosphorique présentant une concentration d'au moins 75 % en masse, l'acide chlorhydrique présentant une concentration d'au moins 30 % en masse. It is thus possible to use, as concentrated acid, sulfuric acid having a concentration of at least 1400 g / l, in particular at least 1650 g / l. Thus, according to one of the essential characteristics of the variant (B), taken in combination with a sequence of steps with specific conditions, in particular a certain concentration of alkali metal silicate, as well as a ratio of amount of silicate added (expressed in S1O2) / amount of silicate present in the initial stock (expressed in S1O2) appropriate, the acid used in a part of step (iii), preferably in step (iii) (this is in all of step (iii)), is a concentrated acid, preferably selected from the group consisting of sulfuric acid having a concentration of at least 80% by weight, in particular at least 90% by weight. % by mass, acetic acid or formic acid having a concentration of at least 90% by weight, the nitric acid having a concentration of at least 60% by weight, the phosphoric acid having a concentration of at least 75% by mass, hydrochloric acid having a concentration of at least 30% by mass.
De manière avantageuse, ledit acide concentré est de l'acide sulfurique concentré, c'est-à-dire de l'acide sulfurique présentant une concentration d'au moins 80 % en masse (et en général d'au plus 98 % en masse), de préférence d'au moins 90 % en masse ; en particulier, sa concentration est comprise entre 90 et 98 % en masse, par exemple entre 91 et 97 % en masse. Selon un mode de réalisation de la variante (B), l'acide concentré tel que défini ci-dessus est utilisé uniquement dans l'étape (iii).  Advantageously, said concentrated acid is concentrated sulfuric acid, that is to say sulfuric acid having a concentration of at least 80% by weight (and generally at most 98% by weight). ), preferably at least 90% by weight; in particular, its concentration is between 90 and 98% by weight, for example between 91 and 97% by weight. According to one embodiment of variant (B), the concentrated acid as defined above is used only in step (iii).
L'acide utilisé dans les étapes (ii), (iv) et (v) peut alors être par exemple un acide dilué, de manière avantageuse de l'acide sulfurique dilué, c'est-à-dire présentant une concentration très inférieure à 80 % en masse, en l'occurrence une concentration inférieure à 20 % en masse (et en général d'au moins 4 % en masse), en particulier inférieure à 14 % en masse, notamment d'au plus 10 % en masse, par exemple comprise entre 5 et 10 % en masse.  The acid used in steps (ii), (iv) and (v) can then be for example a dilute acid, advantageously dilute sulfuric acid, that is to say having a concentration much lower than 80% by weight, in this case a concentration of less than 20% by weight (and in general of at least 4% by weight), in particular less than 14% by weight, especially not more than 10% by weight, for example between 5 and 10% by weight.
De préférence, l'acide utilisé dans l'étape (iv) est également un acide concentré tel que mentionné ci-dessus. Preferably, the acid used in step (iv) is also a concentrated acid as mentioned above.
Cependant, selon un mode de réalisation préféré de la variante (B), l'acide utilisé dans les étapes (iv) et (v) est également un acide concentré tel que mentionné ci-dessus. However, according to a preferred embodiment of variant (B), the acid used in steps (iv) and (v) is also a concentrated acid as mentioned above.
Dans le cadre de ce mode de réalisation préféré de la variante (B), l'acide utilisé dans la totalité de l'étape (ii) peut alors être par exemple un acide dilué comme décrit ci-dessus, il peut être avantageux, dans cette variante de l'invention, que dans au moins une partie de l'étape (ii), en général dans une deuxième et dernière partie de cette étape (ii), l'acide utilisé soit également un acide concentré tel que mentionné ci-dessus (l'acide utilisé dans l'autre partie de l'étape (ii) étant par exemple un acide dilué comme décrit ci-dessus). Dans le cadre de ce mode de réalisation préféré de la variante (B), l'acide utilisé dans la totalité de l'étape (ii) peut également être un acide concentré tel que mentionné ci-dessus, de manière avantageuse de l'acide sulfurique concentré, c'est-à-dire présentant une concentration d'au moins 80 % en masse, de préférence d'au moins 90 % en masse, en particulier comprise entre 90 et 98 % en masse. De préférence, dans le cas de cette utilisation on ajoute de l'eau dans le pied de cuve initial, en particulier soit avant l'étape (ii) soit au cours de l'étape (ii). In the context of this preferred embodiment of variant (B), the acid used in the whole of step (ii) may then be for example a diluted acid as described above, it may be advantageous, in this variant of the invention, that in at least a part of step (ii), in general in a second and last part of this step (ii), the acid used is also a concentrated acid as mentioned above (the acid used in the other part of step (ii) being for example a diluted acid such as described above). In the context of this preferred embodiment of variant (B), the acid used in the whole of step (ii) may also be a concentrated acid as mentioned above, advantageously acid concentrated sulfuric acid, that is to say having a concentration of at least 80% by weight, preferably at least 90% by weight, in particular between 90 and 98% by weight. Preferably, in the case of this use is added water in the initial stock, especially before step (ii) or during step (ii).
Dans le procédé selon l'invention, le choix de l'acide, de l'éventuel agent alcalin et du silicate de métal alcalin M se fait d'une manière bien connue en soi. In the process according to the invention, the choice of the acid, the optional alkaline agent and the alkali metal silicate M is in a manner well known per se.
On utilise généralement comme acide(s) (acide concentré ou acide dilué) un acide organique tel que l'acide acétique, l'acide formique ou l'acide carbonique ou, de préférence, un acide minéral tel que l'acide sulfurique, l'acide nitrique, l'acide phosphorique ou l'acide chlorhydrique.  The acid (s) (concentrated acid or dilute acid) is generally an organic acid such as acetic acid, formic acid or carbonic acid or, preferably, a mineral acid such as sulfuric nitric acid, phosphoric acid or hydrochloric acid.
Si on utilise comme acide concentré de l'acide acétique concentré ou de l'acide formique concentré, alors leur concentration est d'au moins 90 % en masse.  If concentrated acetic acid or concentrated formic acid is used as the concentrated acid, then their concentration is at least 90% by weight.
Si on utilise comme acide concentré de l'acide nitrique concentré, alors sa concentration est d'au moins 60 % en masse.  If concentrated nitric acid is used as concentrated acid, then its concentration is at least 60% by weight.
Si on utilise comme acide concentré de l'acide phosphorique concentré, alors sa concentration est d'au moins 75 % en masse.  If concentrated concentrated phosphoric acid is used, then its concentration is at least 75% by weight.
Si on utilise comme acide concentré de l'acide chlorhydrique concentré, alors sa concentration est d'au moins 30 % en masse.  If concentrated hydrochloric acid is used as concentrated acid, then its concentration is at least 30% by weight.
Cependant, de manière très avantageuse, on emploie comme acide(s) un (des) acide(s) sulfurique(s), l'acide sulfurique concentré alors utilisé présentant une concentration telle que déjà mentionnée dans l'exposé ci-dessus.  However, very advantageously, the acid (s) used is sulfuric acid (s), the concentrated sulfuric acid then used having a concentration as already mentioned in the above discussion.
En général, lorsque de l'acide concentré est utilisé dans plusieurs étapes, on emploie alors le même acide concentré. On peut par ailleurs utiliser en tant que silicate toute forme courante de silicates tels que métasilicates, disilicates et avantageusement un silicate de métal alcalin M dans lequel M est le sodium ou le potassium. Le silicate peut présenter une concentration (exprimée en S1O2) comprise entre 2 et 330 g/L, par exemple entre 3 et 300 g/L, en particulier entre 4 et 260 g/L. In general, when concentrated acid is used in several steps, then the same concentrated acid is used. It is also possible to use, as silicate, any common form of silicates such as metasilicates, disilicates and advantageously an alkali metal silicate M in which M is sodium or potassium. The silicate may have a concentration (expressed as SiO 2) of between 2 and 330 g / l, for example between 3 and 300 g / l, in particular between 4 and 260 g / l.
De manière générale, on emploie, comme silicate, le silicate de sodium. Dans le cas où l'on utilise le silicate de sodium, celui-ci présente, en général, un rapport pondéral SiO2/Na2O compris entre 2,5 et 4, par exemple entre 3,2 et 3,8.  In general, the silicate used is sodium silicate. In the case where sodium silicate is used, it generally has a weight ratio SiO 2 / Na 2 O of between 2.5 and 4, for example between 3.2 and 3.8.
L'agent alcalin employé lors de l'éventuelle étape (vi) peut être par exemple une solution de soude, de potasse ou d'ammoniac. De préférence, cet agent alcalin est du silicate, en particulier du silicate tel qu'utilisé lors des étapes précédentes.  The alkaline agent employed in the optional step (vi) may be, for example, a solution of sodium hydroxide, potassium hydroxide or ammonia. Preferably, this alkaline agent is silicate, in particular silicate as used in the preceding steps.
Dans le procédé de préparation de l'invention, la réaction du silicate avec l'acide se fait d'une manière très spécifique selon les étapes suivantes. In the preparation process of the invention, the reaction of the silicate with the acid is in a very specific manner according to the following steps.
On forme tout d'abord (étape (i)) un pied de cuve aqueux qui comprend du silicate. First (step (i)) is formed an aqueous stock which comprises silicate.
La concentration en silicate (exprimée en S1O2) de ce pied de cuve initial est inférieure à 20 g/L.  The silicate concentration (expressed in S102) of this initial base stock is less than 20 g / l.
Cette concentration est de préférence d'au plus 15 g/L, en particulier d'au plus 1 1 g/L, par exemple d'au plus 8 g/L.  This concentration is preferably at most 15 g / l, in particular at most 1 1 g / l, for example at most 8 g / l.
Le pied de cuve formé dans l'étape (i) peut éventuellement comprendre un électrolyte. Néanmoins, de préférence, aucun électrolyte n'est ajouté au cours du procédé de préparation, en particulier dans l'étape (i).  The vessel stock formed in step (i) may optionally comprise an electrolyte. Nevertheless, preferably, no electrolyte is added during the preparation process, in particular in step (i).
Le terme d'électrolyte s'entend ici dans son acceptation normale, c'est-à-dire qu'il signifie toute substance ionique ou moléculaire qui, lorsqu'elle est en solution, se décompose ou se dissocie pour former des ions ou des particules chargées. On peut citer comme électrolyte un sel du groupe des sels des métaux alcalins et alcalino-terreux, notamment le sel du métal de silicate de départ et de l'acide, par exemple le chlorure de sodium dans le cas de la réaction d'un silicate de sodium avec l'acide chlorhydrique ou, de préférence, le sulfate de sodium dans le cas de la réaction d'un silicate de sodium avec l'acide sulfurique.  The term electrolyte is here understood in its normal acceptation, that is to say that it signifies any ionic or molecular substance which, when in solution, decomposes or dissociates to form ions or charged particles. As electrolyte, mention may be made of a salt of the group of alkali and alkaline earth metal salts, in particular the salt of the starting silicate metal and of the acid, for example sodium chloride in the case of the reaction of a silicate of sodium with hydrochloric acid or, preferably, sodium sulfate in the case of the reaction of a sodium silicate with sulfuric acid.
La deuxième étape (étape (ii)) consiste à ajouter de l'acide dans le pied de cuve initial. The second step (step (ii)) is to add acid in the initial stock.
Ainsi, dans cette deuxième étape, on ajoute de l'acide audit pied de cuve initial jusqu'à ce qu'au moins 50 %, en particulier 50 à 99 %, de la quantité de M2O présente dans ledit pied de cuve initial soient neutralisés. Une fois qu'est atteinte la valeur souhaitée de quantité de M2O neutralisé, on procède alors à une addition simultanée (étape (Ni)) d'acide et d'une quantité de silicate de métal alcalin M telle que le taux de consolidation, c'est-à-dire le rapport quantité de silicate ajoutée (exprimée en SiO2) / quantité de silicate présente dans le pied de cuve initial (exprimée en SiO2) soit supérieur à 4 et d'au plus 100. Thus, in this second step, acid is added to said initial base stock until at least 50%, in particular 50% to 99%, of the quantity of M 2 O present in said initial base stock. neutralized. Once the desired value of the amount of neutralized M 2 O has been reached, a simultaneous addition (step (Ni)) of acid and an amount of alkali metal silicate M such as the consolidation rate are then carried out. , that is to say the ratio amount of silicate added (expressed as SiO 2 ) / amount of silicate present in the initial stock (expressed in SiO 2 ) is greater than 4 and at most 100.
Selon une variante du procédé de l'invention, on procède à cette addition simultanée d'acide et d'une quantité de silicate de métal alcalin M de telle manière que le taux de consolidation soit de préférence compris entre 12 et 100, en particulier entre 12 et 50, notamment entre 13 et 40.  According to one variant of the process of the invention, this simultaneous addition of acid and a quantity of alkali metal silicate M is carried out so that the consolidation ratio is preferably between 12 and 100, in particular between 12 and 50, especially between 13 and 40.
Selon une autre variante du procédé de l'invention, on procède à cette addition simultanée d'acide et d'une quantité de silicate de métal alcalin M de telle manière que le taux de consolidation soit plutôt supérieur à 4 et inférieur à 12, en particulier compris entre 5 et 1 1 ,5, notamment entre 7,5 et 1 1 . Cette variante est, en général, mise en œuvre quand la concentration en silicate dans le pied de cuve initial est d'au moins 8 g/L, en particulier comprise entre 10 et 15 g/L, par exemple entre 1 1 et 15 g/L.  According to another variant of the process of the invention, this simultaneous addition of acid and a quantity of alkali metal silicate M is carried out in such a way that the consolidation ratio is rather greater than 4 and less than 12, particular between 5 and 1 1, 5, especially between 7.5 and 1 1. This variant is, in general, implemented when the silicate concentration in the initial stock is at least 8 g / l, in particular between 10 and 15 g / l, for example between 11 and 15 g. / L.
De manière préférée, pendant toute l'étape (iii), la quantité d'acide ajoutée est telle que 80 à 99 %, par exemple 85 à 97 %, de la quantité de M2O ajoutée soient neutralisés. Preferably, during the entire step (iii), the amount of added acid is such that 80 to 99%, for example 85 to 97%, of the amount of M 2 O added are neutralized.
Dans l'étape (iii), il est possible de procéder à l'addition simultanée d'acide et de silicate à un premier palier de pH du milieu réactionnel, ρΗ-ι, puis à un second palier de pH du milieu réactionnel, pH2, tel que 7 < pH2 < pHi < 9. In step (iii), it is possible to proceed to the simultaneous addition of acid and silicate at a first pH level of the reaction medium, ρΗ-ι, then at a second pH level of the reaction medium, pH 2 , such as 7 <pH 2 <pHi <9.
Ensuite, dans une étape (iv), on arrête l'addition du silicate tout en continuant l'addition d'acide dans le milieu réactionnel de manière à obtenir une valeur du pH du milieu réactionnel comprise entre 2,5 et 5,3 (par exemple entre 3,0 et 5,3), de préférence entre 2,8 et 5,2 (par exemple entre 4,0 et 5,2), en particulier entre 3,5 et 5,1 (voire entre 3,5 et 5,0). Then, in a step (iv), the addition of the silicate is stopped while continuing the addition of acid in the reaction medium so as to obtain a pH value of the reaction medium of between 2.5 and 5.3 ( for example between 3.0 and 5.3), preferably between 2.8 and 5.2 (for example between 4.0 and 5.2), in particular between 3.5 and 5.1 (or even between 3, 5 and 5.0).
On peut éventuellement effectuer juste après cette étape (iv) un mûrissement du milieu réactionnel, notamment au pH obtenu à l'issue de l'étape (iv), et en général sous agitation ; ce mûrissement peut par exemple durer de 2 à 45 minutes, en particulier de 5 à 20 minutes et ne comporte préférentiellement ni addition d'acide, ni addition de silicate.  It is possible to carry out, just after this step (iv), a ripening of the reaction medium, in particular at the pH obtained after step (iv), and in general with stirring; this curing can for example last from 2 to 45 minutes, in particular from 5 to 20 minutes, and preferably does not include any addition of acid or addition of silicate.
Puis on met en contact (étape (v)) - le milieu réactionnel obtenu à l'issue de l'étape (iv), ledit milieu réactionnel présentant ainsi un pH compris entre 2,5 et 5,3, de préférence entre 2,8 et 5,2, par exemple entre 3,5 et 5,1 (voire entre 3,5 et 5,0), Then we put in contact (step (v)) the reaction medium obtained at the end of stage (iv), said reaction medium thus having a pH of between 2.5 and 5.3, preferably between 2.8 and 5.2, for example between 3, 5 and 5.1 (or between 3.5 and 5.0),
- avec de l'acide et du silicate (en particulier du silicate de métal alcalin M), de telle manière (en particulier à des débits tels) que le pH du milieu réactionnel obtenu soit maintenu entre 2,5 et 5,3 (par exemple entre 3,0 et 5,3), de préférence entre 2,8 et 5,2 (par exemple entre 4,0 et 5,2), par exemple entre 3,5 et 5,1 (voire entre 3,5 et 5,0).  with acid and silicate (in particular alkali metal silicate M), in such a way (particularly at such rates) that the pH of the reaction medium obtained is maintained between 2.5 and 5.3 (by between 3.0 and 5.3), preferably between 2.8 and 5.2 (for example between 4.0 and 5.2), for example between 3.5 and 5.1 (or even 3.5 and 5.0).
Ledit pH du milieu réactionnel peut varier à l'intérieur de la plage 2,5-5,3, de préférence de la plage 2,8-5,2, par exemple de la plage 3,5-5,1 (voire 3,5-5,0), ou, de manière préférée, rester (sensiblement) constant à l'intérieur de ces plages.  Said pH of the reaction medium may vary within the range 2.5-5.3, preferably in the range 2.8-5.2, for example in the range 3.5-5.1 (even 3 , 5-5,0), or, preferably, remain (substantially) constant within these ranges.
En général, dans cette étape (v), la mise en contact du milieu réactionnel issu de l'étape (iv) avec l'acide et le silicate (par exemple le silicate de métal alcalin M) est effectuée en ajoutant de l'acide et du silicate audit milieu réactionnel.  In general, in this step (v), the contacting of the reaction medium resulting from step (iv) with the acid and the silicate (for example the alkali metal silicate M) is carried out by adding acid. and silicate said reaction medium.
Selon une variante du procédé de l'invention, dans l'étape (v), on ajoute audit milieu réactionnel d'abord l'acide, puis le silicate.  According to a variant of the process of the invention, in step (v), the acid and then the silicate are added to said reaction medium.
Cependant, selon une variante préférée du procédé de l'invention, dans l'étape (v), on ajoute plutôt simultanément l'acide et le silicate (par exemple le silicate de métal alcalin M) audit milieu réactionnel ; de préférence, cette addition simultanée est effectuée avec régulation du pH du milieu réactionnel obtenu lors de cette addition à une valeur (sensiblement) constante à l'intérieur des plages précitées.  However, according to a preferred variant of the process of the invention, in step (v), the acid and the silicate (for example the alkali metal silicate M) are added simultaneously to said reaction medium; preferably, this simultaneous addition is carried out with regulation of the pH of the reaction medium obtained during this addition to a value (substantially) constant within the aforementioned ranges.
L'étape (v) est généralement effectuée sous agitation.  Step (v) is generally carried out with stirring.
L'éventuelle étape (vi) du procédé selon l'invention consiste en une addition, dans le milieu réactionnel obtenu à l'issue de l'étape (v), d'un agent alcalin, de préférence de silicate (en particulier de silicate de métal alcalin M), et ce jusqu'à atteindre une valeur du pH du milieu réactionnel comprise entre 4,7 et 6,3, de préférence entre 5,0 et 5,8, par exemple entre 5,0 et 5,4. The optional step (vi) of the process according to the invention consists of an addition, in the reaction medium obtained at the end of step (v), of an alkaline agent, preferably of silicate (in particular of silicate of alkali metal M), until a pH value of the reaction medium is between 4.7 and 6.3, preferably between 5.0 and 5.8, for example between 5.0 and 5.4. .
Cette étape (vi) est habituellement effectuée sous agitation.  This step (vi) is usually carried out with stirring.
En général, l'ensemble de la réaction (étapes (i) à (v), ou (vi) le cas échéant) est effectué sous agitation. In general, the whole reaction (steps (i) to (v), or (vi) if necessary) is carried out with stirring.
Toutes les étapes (i) à (v), ou (vi) le cas échéant sont habituellement réalisées entre 75 et 97 °C, de préférence entre 80 et 96 °C. Selon une variante du procédé de l'invention, l'ensemble des étapes est effectué à une température constante. All steps (i) to (v), or (vi) where appropriate are usually carried out between 75 and 97 ° C, preferably between 80 and 96 ° C. According to a variant of the process of the invention, all the steps are carried out at a constant temperature.
Selon une autre variante du procédé de l'invention, que l'étape (ii) soit effectuée (en totalité ou en partie) ou ne soit pas effectuée avec de l'acide concentré, la température de fin de réaction est plus élevée que la température de début de réaction : ainsi, on maintient la température au début de la réaction (par exemple au cours des étapes (i) et (ii)) de préférence entre 75 et 90 °C, puis on augmente la température, de préférence jusqu'à une valeur comprise entre 90 et 97 °C, valeur à laquelle elle est maintenue (par exemple au cours des étapes (iii) à (vi)) jusqu'à la fin de la réaction.  According to another variant of the process of the invention, whether step (ii) is carried out (in whole or in part) or is not carried out with concentrated acid, the end-of-reaction temperature is higher than the Reaction start temperature: thus, the temperature is maintained at the start of the reaction (for example during steps (i) and (ii)) preferably between 75 and 90 ° C, then the temperature is increased, preferably until at a value between 90 and 97 ° C, the value at which it is maintained (for example during steps (iii) to (vi)) until the end of the reaction.
Il peut être avantageux de procéder à l'issue de l'étape (v), ou de l'éventuelle étape (vi) à un mûrissement du milieu réactionnel obtenu, notamment au pH obtenu à l'issue de cette étape (v) (ou de l'étape (vi)), et en général sous agitation. Ce mûrissement peut par exemple durer de 2 à 30 minutes, en particulier de 3 à 20 minutes et peut être réalisé entre 75 et 97 °C, de préférence entre 80 et 96 °C, en particulier à la température à laquelle a été effectuée l'étape (v) (ou l'étape (vi)). Il ne comporte préférentiellement ni addition d'acide, ni addition de silicate. It may be advantageous to proceed at the end of step (v) or of the optional step (vi) to a maturation of the reaction medium obtained, in particular at the pH obtained at the end of this step (v) ( or step (vi)), and in general with stirring. This curing can for example last from 2 to 30 minutes, in particular from 3 to 20 minutes and can be carried out between 75 and 97 ° C., preferably between 80 and 96 ° C., in particular at the temperature at which the reaction was carried out. step (v) (or step (vi)). It preferably does not include any addition of acid or addition of silicate.
Dans le procédé selon l'invention, l'étape (v) peut être effectuée dans un mélangeur rapide ou dans une zone d'écoulement turbulent, ce qui peut permettre un meilleur contrôle des caractéristiques des silices précipitées obtenues. In the process according to the invention, step (v) may be carried out in a fast mixer or in a turbulent flow zone, which may allow better control of the characteristics of the precipitated silicas obtained.
Par exemple, dans le cas où, dans l'étape (v), on ajoute au milieu réactionnel obtenu à l'issue de l'étape (iv) d'abord l'acide, puis le silicate (par exemple du silicate de métal alcalin M), alors la mise en contact dudit silicate avec le milieu résultant de l'ajout de l'acide au milieu réactionnel obtenu à l'issue de l'étape (iv) peut être effectuée dans un mélangeur rapide ou dans une zone d'écoulement turbulent.  For example, in the case where, in step (v), the acid then the silicate (for example metal silicate) is added to the reaction mixture obtained at the end of step (iv). alkali M), then the contacting of said silicate with the medium resulting from the addition of the acid to the reaction medium obtained at the end of step (iv) can be carried out in a fast mixer or in a zone d turbulent flow.
De même, dans le cas où, dans l'étape (v), on ajoute simultanément l'acide et le silicate (par exemple du silicate de métal alcalin M) au milieu réactionnel obtenu à l'issue de l'étape (iv), alors la mise en contact dudit acide et dudit silicate avec ledit milieu réactionnel peut être effectuée dans un mélangeur rapide ou dans une zone d'écoulement turbulent.  Similarly, in the case where, in step (v), the acid and the silicate (for example alkali metal silicate M) are added simultaneously to the reaction medium obtained at the end of step (iv). , then bringing said acid and said silicate into contact with said reaction medium can be carried out in a fast mixer or in a turbulent flow zone.
De préférence, le milieu réactionnel obtenu dans le mélangeur rapide ou dans une zone d'écoulement turbulent alimente un réacteur, de préférence soumis à une agitation, réacteur dans lequel l'éventuelle étape (vi) est mise en œuvre. Preferably, the reaction medium obtained in the fast mixer or in a turbulent flow zone feeds a reactor, preferably subjected to agitation, reactor in which the optional step (vi) is implemented.
Dans l'étape (v), on peut utiliser un mélangeur rapide choisi parmi les mélangeurs (ou tubes) en T ou en Y symétriques, les mélangeurs (ou tubes) en T ou en Y asymétriques, les mélangeurs à jets tangentiels, les mélangeurs Hartridge-Roughton, les mélangeurs vortex, les mélangeurs rotor-stators.  In step (v), it is possible to use a fast mixer chosen from symmetrical T or Y mixers, asymmetrical T or Y mixers, tangential jet mixers and mixers. Hartridge-Roughton, vortex mixers, rotor-stator mixers.
Les mélangeurs (ou tubes) en T ou en Y symétriques sont généralement constitués de deux tubes opposés (tubes en T) ou formant un angle inférieur à 180° (tubes en Y), de même diamètre, déchargeant dans un tube central dont le diamètre est identique ou supérieur à celui des deux tubes précédents. Ils sont dits « symétriques » car les deux tubes d'injection des réactifs présentent le même diamètre et le même angle par rapport au tube central, le dispositif étant caractérisé par un axe de symétrie. De préférence, le tube central présente un diamètre deux fois plus élevés environ que le diamètre des tubes opposés ; de même la vitesse de fluide dans le tube central est de préférence égale à la moitié de celle dans les tubes opposés.  Mixers (or tubes) in T or symmetrical Y are usually made of two opposite tubes (T-tubes) or forming an angle less than 180 ° (Y-tubes), of the same diameter, discharging into a central tube whose diameter is identical to or greater than that of the two previous tubes. They are called "symmetrical" because the two reagent injection tubes have the same diameter and the same angle with respect to the central tube, the device being characterized by an axis of symmetry. Preferably, the central tube has a diameter about twice as large as the diameter of the opposed tubes; similarly the fluid velocity in the central tube is preferably half that in the opposite tubes.
On préfère cependant employer, en particulier lorsque les deux fluides à introduire ne présentent pas le même débit, un mélangeur (ou tube) en T ou en Y asymétriques plutôt qu'un mélangeur (ou tube) en T ou en Y symétrique. Dans les dispositifs asymétriques, un des fluides (le fluide de plus faible débit en général) est injecté dans le tube central au moyen d'un tube latéral de diamètre plus faible. Ce dernier forme avec le tube central un angle de 90° en général (tube en T) ; cet angle peut être différent de 90° (tube en Y), donnant des systèmes à co-courant (par exemple angle de 45°) ou à contre-courant (par exemple angle de 135°) par rapport à l'autre courant.  However, it is preferred to use, particularly when the two fluids to be introduced do not have the same flow rate, an asymmetrical T-shaped or Y-shaped mixer (or tube) rather than a symmetrical T-shaped or Y-shaped mixer (or tube). In asymmetric devices, one of the fluids (the lower flow fluid in general) is injected into the central tube by means of a smaller diameter side tube. The latter forms with the central tube an angle of 90 ° in general (T-tube); this angle may be different from 90 ° (Y-tube), giving co-current systems (for example 45 ° angle) or counter-current (for example 135 ° angle) relative to the other current.
A titre de mélangeur rapide, on utilise de préférence un mélangeur à jets tangentiels, un mélangeur Hartridge-Roughton ou un mélangeur (ou précipiteur) vortex, qui dérivent des dispositifs en T symétriques.  As a fast mixer, a tangential jet mixer, a Hartridge-Roughton mixer or a vortex mixer (or precipitator) are preferably used, which are derived from symmetrical T-shaped devices.
Plus particulièrement, dans l'étape (v), on peut mettre en œuvre un mélangeur rapide à jets tangentiels, Hartridge-Roughton ou vortex, comprenant une chambre ayant (a) au moins deux admissions tangentielles par lesquelles entrent séparément (mais en même temps) soit, d'une part, le silicate, et, d'autre part, le milieu résultant de l'ajout d'acide au milieu réactionnel issu de l'étape (iv), soit, d'une part, le silicate et l'acide, et, d'autre part, le milieu réactionnel issu de l'étape (iv), et (b) une sortie axiale par laquelle sort le milieu réactionnel obtenu dans cette étape (v) et ce, de préférence, vers un(e) réacteur (cuve) disposé(e) en série après ledit mélangeur. Les deux admissions tangentielles sont de préférence situées symétriquement, et de manière opposée, par rapport à l'axe central de ladite chambre. More particularly, in step (v), it is possible to use a tangential jet fast mixer, Hartridge-Roughton or vortex, comprising a chamber having (a) at least two tangential admissions through which enter separately (but at the same time ) on the one hand, the silicate, and on the other hand, the medium resulting from the addition of acid to the reaction medium resulting from step (iv), namely, on the one hand, silicate and the acid, and on the other hand, the reaction medium resulting from step (iv), and (b) an axial outlet through which the reaction medium obtained in this step (v) leaves, preferably to a reactor (tank) arranged in series after said mixer. The two tangential admissions are of preferably located symmetrically and oppositely to the central axis of said chamber.
La chambre du mélangeur à jets tangentiels, Hartridge-Roughton ou vortex éventuellement utilisé présente généralement une section circulaire et est de préférence de forme cylindrique.  The mixer chamber with tangential jets, Hartridge-Roughton or vortex optionally used generally has a circular section and is preferably of cylindrical shape.
Chaque tube d'admission tangentielle peut présenter un diamètre interne d de 0,5 à 80 mm.  Each tangential inlet tube may have an internal diameter d of 0.5 to 80 mm.
Ce diamètre interne d peut être compris entre 0,5 et 10 mm, en particulier entre 1 et 9 mm, par exemple entre 2 et 7 mm. Cependant, notamment à l'échelle industrielle, il est de préférence compris entre 10 et 80 mm, en particulier entre 20 et 60 mm, par exemple entre 30 et 50 mm.  This internal diameter d may be between 0.5 and 10 mm, in particular between 1 and 9 mm, for example between 2 and 7 mm. However, especially on an industrial scale, it is preferably between 10 and 80 mm, in particular between 20 and 60 mm, for example between 30 and 50 mm.
Le diamètre interne de la chambre du mélangeur à jets tangentiels, Hartridge-Roughton ou vortex éventuellement employé peut être compris entre 3d et 6d, en particulier entre 3d et 5d, par exemple égal à 4d ; le diamètre interne du tube de sortie axiale peut être compris entre 1 d et 3d, en particulier entre 1 ,5d et 2,5d, par exemple égal à 2d.  The internal diameter of the chamber of the tangential jet mixer, Hartridge-Roughton or vortex optionally used may be between 3d and 6d, in particular between 3d and 5d, for example equal to 4d; the internal diameter of the axial outlet tube may be between 1 d and 3d, in particular between 1.5d and 2.5d, for example equal to 2d.
Les débits du silicate et de l'acide sont par exemple déterminés de façon à ce qu'au point de confluence les deux courants de réactifs entrent en contact l'un avec l'autre dans une zone d'écoulement suffisamment turbulent.  The flow rates of the silicate and the acid are for example determined so that at the confluence point the two reactant streams come into contact with each other in a sufficiently turbulent flow zone.
Dans le procédé selon l'invention, on obtient, à l'issue de l'étape (v) (ou de l'étape (vi) le cas échéant), éventuellement suivie d'un mûrissement, une bouillie de silice qui est ensuite séparée (séparation liquide-solide). In the process according to the invention, at the end of step (v) (or of step (vi) if appropriate), a silica slurry is obtained, which is optionally followed by maturing. separated (liquid-solid separation).
La séparation mise en œuvre dans le procédé de préparation selon l'invention comprend habituellement une filtration, suivie d'un lavage si nécessaire. La filtration s'effectue selon toute méthode convenable, par exemple au moyen d'un filtre presse, d'un filtre à bande, d'un filtre sous vide.  The separation used in the preparation process according to the invention usually comprises a filtration, followed by washing if necessary. The filtration is carried out by any suitable method, for example by means of a filter press, a belt filter, a vacuum filter.
La suspension de silice ainsi récupérée (gâteau de filtration) est ensuite séchée.  The silica suspension thus recovered (filter cake) is then dried.
Ce séchage peut se faire selon tout moyen connu en soi.  This drying can be done by any means known per se.
De préférence, le séchage se fait par atomisation. A cet effet, on peut utiliser tout type d'atomiseur convenable, notamment un atomiseur à turbines, à buses, à pression liquide ou à deux fluides. En général, lorsque la filtration est effectuée à l'aide d'un filtre presse, on utilise un atomiseur à buses, et, lorsque la filtration est effectuée à l'aide d'un filtre sous-vide, on utilise un atomiseur à turbines.  Preferably, the drying is done by atomization. For this purpose, any suitable type of atomizer may be used, such as a turbine, nozzle, liquid pressure or two-fluid atomizer. In general, when the filtration is carried out using a filter press, a nozzle atomizer is used, and when the filtration is carried out using a vacuum filter, a turbine atomizer is used. .
Il y a lieu de noter que le gâteau de filtration n'est pas toujours dans des conditions permettant une atomisation notamment à cause de sa viscosité élevée. D'une manière connue en soi, on soumet alors le gâteau à une opération de délitage. Cette opération peut être réalisée mécaniquement, par passage du gâteau dans un broyeur de type colloïdal ou à billes. Le délitage est généralement effectué en présence d'eau et/ou en présence d'un composé de l'aluminium, en particulier d'aluminate de sodium et, éventuellement, en présence d'un acide tel que décrit précédemment (dans ce dernier cas, le composé de l'aluminium et l'acide sont généralement ajoutés de manière simultanée).It should be noted that the filter cake is not always under conditions allowing atomization, in particular because of its viscosity. high. In a manner known per se, the cake is then subjected to a disintegration operation. This operation can be performed mechanically, by passing the cake in a colloid mill or ball. The disintegration is generally carried out in the presence of water and / or in the presence of an aluminum compound, in particular sodium aluminate and, optionally, in the presence of an acid as described above (in the latter case the aluminum compound and the acid are usually added simultaneously).
L'opération de délitage permet notamment d'abaisser la viscosité de la suspension à sécher ultérieurement. The disintegration operation makes it possible in particular to lower the viscosity of the suspension to be dried later.
Lorsque le séchage est effectué à l'aide d'un atomiseur à buses, la silice susceptible d'être alors obtenue se présente habituellement sous forme de billes sensiblement sphériques.  When the drying is carried out using a nozzle atomizer, the silica that can then be obtained is usually in the form of substantially spherical balls.
A l'issue du séchage, on peut alors procéder à une étape de broyage sur le produit récupéré. La silice qui est alors susceptible d'être obtenue se présente généralement sous forme d'une poudre.  At the end of the drying, it is then possible to carry out a grinding step on the recovered product. The silica that is then likely to be obtained is generally in the form of a powder.
Lorsque le séchage est effectué à l'aide d'un atomiseur à turbines, la silice susceptible d'être alors obtenue peut se présenter sous la forme d'une poudre.  When the drying is carried out using a turbine atomizer, the silica that may then be obtained may be in the form of a powder.
Enfin, le produit séché (notamment par un atomiseur à turbines) ou broyé tel qu'indiqué précédemment peut éventuellement être soumis à une étape d'agglomération, qui consiste par exemple en une compression directe, une granulation voie humide (c'est-à-dire avec utilisation d'un liant tel que eau, suspension de silice ...), une extrusion ou, de préférence, un compactage à sec. Finally, the dried product (in particular by a turbine atomizer) or milled as indicated above may optionally be subjected to an agglomeration step, which consists, for example, of a direct compression, a wet-path granulation (that is, with the use of a binder such as water, silica suspension, etc.), extrusion or, preferably, dry compaction.
Lorsque l'on met en œuvre cette dernière technique, il peut s'avérer opportun, avant de procéder au compactage, de désaérer (opération appelée également pré-densification ou dégazage) les produits pulvérulents de manière à éliminer l'air inclus dans ceux-ci et assurer un compactage plus régulier. When the latter technique is used, it may be advisable, before compacting, to deaerate (operation also called pre-densification or degassing) the pulverulent products so as to eliminate the air included in these products. ci and ensure a more regular compaction.
La silice susceptible d'être alors obtenue par cette étape d'agglomération se présente généralement sous la forme de granulés.  The silica that can then be obtained by this agglomeration step is generally in the form of granules.
Les poudres, de même que les billes, de silice obtenues par le procédé selon l'invention offrent ainsi l'avantage, entre autres, d'accéder de manière simple, efficace et économique, à des granulés, notamment par des opérations classiques de mise en forme, telles que par exemple une granulation ou un compactage. Les silices précipitées préparées par le procédé selon l'invention se présentent en général sous au moins l'une des formes suivantes : billes sensiblement sphériques, poudre, granulés. De manière générale, le procédé selon l'invention permet d'obtenir des silices formées d'agrégats de grosses particules primaires de silice à la surface desquels se trouvent des petites particules primaires de silice. La mise en œuvre du procédé de préparation selon l'invention, particulièrement lorsque l'acide concentré utilisé est de l'acide sulfurique concentré, permet notamment d'obtenir au cours dudit procédé (à l'issue de l'étape (v) ou de l'éventuelle étape (vi)) une suspension plus concentrée en silice précipitée que celle obtenue par un procédé identique utilisant uniquement de l'acide dilué, et donc un gain en productivité en silice précipitée (pouvant atteindre par exemple au moins 10 à 40 %), en particulier à la réaction de précipitation (c'est-à-dire à l'issue de l'étape (v) ou de l'éventuelle étape (vi)), tout en s'accompagnant de manière surprenante de l'obtention de silices précipitées présentant, de préférence, une morphologie, une granulométrie et une porosité particulières. ; de manière plus générale, les silices précipitées obtenues par le procédé selon l'invention présentent préférentiellement une bonne aptitude à la dispersion dans les polymères et confèrent à ceux-ci un compromis de propriétés satisfaisant, par exemple au niveau de leurs propriétés mécaniques, dynamiques et rhéologiques, comparables à celles des silices précipitées obtenues par un procédé identique mettant en œuvre uniquement de l'acide dilué. The powders, as well as the silica beads, obtained by the process according to the invention thus offer the advantage, among others, of having a simple, effective and economical way of accessing granules, in particular by conventional setting operations. shaped, such as for example granulation or compaction. The precipitated silicas prepared by the process according to the invention are generally in at least one of the following forms: substantially spherical beads, powder, granules. In general, the process according to the invention makes it possible to obtain silicas formed from aggregates of large primary particles of silica, on the surface of which there are small primary particles of silica. The implementation of the preparation method according to the invention, particularly when the concentrated acid used is concentrated sulfuric acid, makes it possible in particular to obtain during said process (at the end of step (v) or of the optional step (vi)) a more concentrated suspension of precipitated silica than that obtained by an identical process using only dilute acid, and therefore a productivity gain in precipitated silica (which can reach for example at least 10 to 40 %), in particular to the precipitation reaction (that is to say at the end of step (v) or of the possible step (vi)), while surprisingly accompanying the obtaining precipitated silicas having, preferably, a particular morphology, particle size and porosity. ; more generally, the precipitated silicas obtained by the process according to the invention preferably have good dispersibility in the polymers and give them a compromise of satisfactory properties, for example in terms of their mechanical, dynamic and rheological, comparable to those precipitated silicas obtained by an identical process using only diluted acid.
De manière avantageuse, dans le même temps, notamment lorsque l'acide concentré utilisé est de l'acide sulfurique concentré, le procédé selon l'invention permet, par rapport à un procédé identique employant uniquement de l'acide dilué, un gain (pouvant atteindre par exemple au moins 15 à 60 %) sur la consommation d'énergie (sous forme de vapeur vive par exemple), en particulier à la réaction de précipitation (c'est-à-dire à l'issue de l'étape (v) ou de l'éventuelle étape (vi)), du fait d'une diminution des quantités d'eau engagées et de l'exo- thermicité liée à l'utilisation d'acide concentré. En outre, l'utilisation d'acide concentré permet de restreindre (par exemple d'au moins 15 %) la quantité d'eau nécessaire à la réaction, notamment du fait de la diminution de la quantité d'eau utilisée pour la préparation de l'acide.  Advantageously, at the same time, especially when the concentrated acid used is concentrated sulfuric acid, the process according to the invention makes it possible, compared to an identical process employing only dilute acid, a gain ( reach for example at least 15 to 60%) on the energy consumption (in the form of live steam for example), in particular the precipitation reaction (that is to say at the end of the step ( v) or possible step (vi)), due to a decrease in the quantities of water involved and the exothermic nature of the use of concentrated acid. In addition, the use of concentrated acid makes it possible to restrict (for example by at least 15%) the quantity of water required for the reaction, in particular because of the reduction in the quantity of water used for the preparation of acid.
La silice précipitée préparée par le procédé selon l'invention peut être mise en œuvre dans diverses applications. Elle peut être employée par exemple comme support de catalyseur, comme absorbant de matières actives (en particulier support de liquides, notamment utilisés dans l'alimentation, tels que les vitamines (vitamine E), le chlorure de choline), dans des compositions de polymère(s), notamment d'élastomère(s), de silicone(s), comme agent viscosant, texturant ou anti-mottant, comme élément pour séparateurs de batteries, additif pour dentifrice, pour béton, pour papier. The precipitated silica prepared by the process according to the invention can be used in various applications. It can be used, for example, as a catalyst support, as an absorbent of active substances (in particular a carrier for liquids, especially used in foodstuffs, such as vitamins (vitamin E), choline chloride), in polymer compositions. (s), in particular elastomer (s), silicone (s), as viscosity agent, texturizing or anti-caking, as an element for battery separators, additive for toothpaste, for concrete, for paper.
Elle peut être employée pour le renforcement des polymères, naturels ou synthétiques. It can be used for reinforcing polymers, natural or synthetic.
Les compositions de polymère(s) dans lesquelles les silices précipitées préparées par le procédé selon l'invention peuvent être utilisées, notamment à titre de charge renforçante, sont en général à base d'un ou plusieurs polymères ou copolymères, en particulier d'un ou plusieurs élastomères, notamment les élastomères thermoplastiques, présentant, de préférence, au moins une température de transition vitreuse comprise entre -150 et +300 °C, par exemple entre -150 et +20 °C.  The polymer compositions in which the precipitated silicas prepared by the process according to the invention can be used, in particular as reinforcing filler, are generally based on one or more polymers or copolymers, in particular a or more elastomers, especially thermoplastic elastomers, preferably having at least a glass transition temperature of between -150 and +300 ° C, for example between -150 and +20 ° C.
A titre de polymères possibles, on peut citer les polymères diéniques, en particulier les élastomères diéniques.  As possible polymers, mention may be made of diene polymers, in particular diene elastomers.
On peut citer, à titre d'exemples, non limitatifs, d'articles finis à base des compositions de polymère(s) décrites précédemment les semelles de chaussures, les pneumatiques, les revêtements de sols, les barrières aux gaz, les matériaux ignifugeants et également les pièces techniques telles que les galets de téléphériques, les joints d'appareils électroménagers, les joints de conduite de liquides ou de gaz, les joints de système de freinage, les tuyaux (flexibles), les gaines (notamment les gaines de câbles), les câbles, les supports de moteur, les bandes de convoyeur et les courroies de transmissions.  By way of non-limiting examples, mention may be made of finished articles based on the polymer compositions described above, such as shoe soles, tires, floor coverings, gas barriers, fireproofing materials and the like. also technical parts such as ropeway rollers, appliance joints, liquid or gas line joints, brake system joints, hoses, ducts (especially cable ducts) , cables, motor mounts, conveyor belts and transmission belts.

Claims

REVENDICATIONS
1 - Procédé de préparation de silice précipitée du type comprenant la réaction d'un silicate de métal alcalin M avec au moins un acide ce par quoi l'on obtient une suspension de silice, puis la séparation et le séchage de cette suspension, dans lequel la réaction du silicate avec l'acide est réalisée de la manière suivante : (i) on forme un pied de cuve aqueux initial comportant du silicate de métal alcalin M, la concentration en silicate (exprimée en S1O2) dudit pied de cuve étant inférieure à 20 g/L, de préférence d'au plus 15 g/L, 1 - Process for the preparation of precipitated silica of the type comprising the reaction of an alkali metal silicate M with at least one acid, whereby a suspension of silica is obtained, and then the separation and drying of this suspension, in which the reaction of the silicate with the acid is carried out in the following manner: (i) an initial aqueous base stock is formed comprising alkali metal silicate M, the silicate concentration (expressed in S102) of said base stock being less than 20 g / L, preferably at most 15 g / L,
(ii) on ajoute de l'acide audit pied de cuve initial, jusqu'à ce qu'au moins 50 % de la quantité de M2O présente dans le dit pied de cuve initial soient neutralisés, (ii) adding acid to said initial stock, until at least 50% of the amount of M 2 O present in said initial stock is neutralized,
(iii) on ajoute au milieu réactionnel, simultanément, du silicate de métal alcalin M et de l'acide, de telle manière que le rapport quantité de silicate ajoutée (exprimée en S1O2) / quantité de silicate présente dans le pied de cuve initial (exprimée en S1O2) soit supérieur à 4 et d'au plus 100, de préférence soit compris entre 12 et 100, en particulier entre 12 et 50, (iii) at the same time, alkali metal silicate M and acid are added to the reaction medium in such a way that the ratio of the amount of silicate added (expressed as SiO 2) / amount of silicate present in the initial base stock ( expressed in S102) is greater than 4 and not more than 100, preferably between 12 and 100, in particular between 12 and 50,
(iv) on arrête l'addition du silicate tout en continuant l'addition de l'acide dans le milieu réactionnel jusqu'à l'obtention d'une valeur du pH du milieu réactionnel comprise entre 2,5 et 5,3, de préférence entre 2,8 et 5,2, (iv) stopping the addition of the silicate while continuing the addition of the acid in the reaction medium until a pH value of the reaction medium of between 2.5 and 5.3 is obtained; preferably between 2.8 and 5.2,
(v) on met en contact le milieu réactionnel avec de l'acide et du silicate, de telle manière que le pH du milieu réactionnel soit maintenu entre 2,5 et 5,3, de préférence entre 2,8 et 5,2, procédé dans lequel : (v) contacting the reaction medium with acid and silicate, such that the pH of the reaction medium is maintained between 2.5 and 5.3, preferably between 2.8 and 5.2, process in which
- dans au moins une partie de l'étape (iii)  in at least a part of step (iii)
et/ou and or
- dans au moins l'étape (v)  in at least step (v)
l'acide utilisé est un acide concentré, de préférence choisi dans le groupe formé par l'acide sulfurique présentant une concentration d'au moins 80 % en masse, en particulier d'au moins 90 % en masse, l'acide acétique ou l'acide formique présentant une concentration d'au moins 90 % en masse, l'acide nitrique présentant une concentration d'au moins 60 % en masse, l'acide phosphorique présentant une concentration d'au moins 75 % en masse, l'acide chlorhydrique présentant une concentration d'au moins 30 % en masse. the acid used is a concentrated acid, preferably selected from the group consisting of sulfuric acid having a concentration of at least 80% by weight, in particular at least 90% by weight, acetic acid or formic acid having a concentration of at least 90% by mass, the nitric acid having a concentration of at least 60% by mass, the phosphoric acid having a concentration of at least 75% by mass, the hydrochloric acid having a concentration of at least 30% by mass.
2- Procédé selon la revendication 1 , caractérisé en ce que, après la mise en contact à l'étape (v) du milieu réactionnel avec de l'acide et du silicate, on ajoute dans le milieu réactionnel obtenu un agent alcalin, de préférence du silicate, et ce de manière à augmenter le pH du milieu réactionnel jusqu'à une valeur comprise entre 4,7 et 6,3, de préférence entre 5,0 et 5,8, 2-Process according to claim 1, characterized in that, after the contacting in step (v) of the reaction medium with acid and silicate, is added in the reaction medium obtained an alkaline agent, preferably silicate, and this so as to increase the pH of the reaction medium to a value between 4.7 and 6.3, preferably between 5.0 and 5.8,
3- Procédé de préparation de silice précipitée du type comprenant la réaction d'un silicate de métal alcalin M avec au moins un acide ce par quoi l'on obtient une suspension de silice, puis la séparation et le séchage de cette suspension, dans lequel la réaction du silicate avec l'acide est réalisée de la manière suivante : 3- A process for the preparation of precipitated silica of the type comprising the reaction of an alkali metal silicate M with at least one acid, whereby a suspension of silica is obtained, and then the separation and drying of this suspension, in which the reaction of the silicate with the acid is carried out as follows:
(i) on forme un pied de cuve aqueux initial comportant du silicate de métal alcalin M, la concentration en silicate (exprimée en S1O2) dudit pied de cuve étant inférieure à 20 g/L, de préférence d'au plus 15 g/L, (i) forming an initial aqueous base stock comprising alkali metal silicate M, the silicate concentration (expressed as SiO 2) of said stock base being less than 20 g / l, preferably at most 15 g / l ,
(ii) on ajoute de l'acide audit pied de cuve initial, jusqu'à ce qu'au moins 50 % de la quantité de M2O présente dans le dit pied de cuve initial soient neutralisés, (ii) adding acid to said initial stock, until at least 50% of the amount of M 2 O present in said initial stock is neutralized,
(iii) on ajoute au milieu réactionnel, simultanément, du silicate de métal alcalin M et de l'acide, de telle manière que le rapport quantité de silicate ajoutée (exprimée en S1O2) / quantité de silicate présente dans le pied de cuve initial (exprimée en S1O2) soit supérieur à 4 et d'au plus 100, de préférence soit compris entre 12 et 100, en particulier entre 12 et 50, (iii) at the same time, alkali metal silicate M and acid are added to the reaction medium in such a way that the ratio of the amount of silicate added (expressed as SiO 2) / amount of silicate present in the initial base stock ( expressed in S102) is greater than 4 and not more than 100, preferably between 12 and 100, in particular between 12 and 50,
(iv) on arrête l'addition du silicate tout en continuant l'addition de l'acide dans le milieu réactionnel jusqu'à l'obtention d'une valeur du pH du milieu réactionnel comprise entre 2,5 et 5,3, de préférence entre 2,8 et 5,2, (iv) stopping the addition of the silicate while continuing the addition of the acid in the reaction medium until a pH value of the reaction medium of between 2.5 and 5.3 is obtained; preferably between 2.8 and 5.2,
(v) on met en contact le milieu réactionnel avec de l'acide et du silicate, de telle manière que le pH du milieu réactionnel soit maintenu entre 2,5 et 5,3, de préférence entre 2,8 et 5,2, procédé dans lequel dans au moins une partie de l'étape (iii) l'acide utilisé est un acide concentré, de préférence choisi dans le groupe formé par l'acide sulfurique présentant une concentration d'au moins 80 % en masse, en particulier d'au moins 90 % en masse, l'acide acétique ou l'acide formique présentant une concentration d'au moins 90 % en masse, l'acide nitrique présentant une concentration d'au moins 60 % en masse, l'acide phosphorique présentant une concentration d'au moins 75 % en masse, l'acide chlorhydrique présentant une concentration d'au moins 30 % en masse. (v) contacting the reaction medium with acid and silicate, such that the pH of the reaction medium is maintained between 2.5 and 5.3, preferably between 2.8 and 5.2, wherein in at least a portion of step (iii) the acid used is a concentrated acid, preferably selected from the group consisting of sulfuric acid having a concentration of at least 80% by weight, in particular at least 90% by weight, the acetic acid or the formic acid having a concentration of at least 90% by mass, the nitric acid having a concentration of at least 60% by mass, the phosphoric acid having a concentration of at least 75% by weight, the hydrochloric acid having a concentration of at least 30% by mass.
4- Procédé selon l'une des revendications 3 et 4 dans lequel dans au moins l'étape (iii), l'acide utilisé est un acide concentré, de préférence choisi dans le groupe formé par l'acide sulfurique présentant une concentration d'au moins 80 % en masse, en particulier d'au moins 90 % en masse, l'acide acétique ou l'acide formique présentant une concentration d'au moins 90 % en masse, l'acide nitrique présentant une concentration d'au moins 60 % en masse, l'acide phosphorique présentant une concentration d'au moins 75 % en masse, l'acide chlorhydrique présentant une concentration d'au moins 30 % en masse. 5- Procédé selon la revendication 3 et 4, caractérisé en ce que, après la mise en contact à l'étape (v) du milieu réactionnel avec de l'acide et du silicate, on ajoute dans le milieu réactionnel obtenu un agent alcalin, de préférence du silicate, et ce de manière à augmenter le pH du milieu réactionnel jusqu'à une valeur comprise entre 4,7 et 6,3, de préférence entre 5,0 et 5,8, 4- Method according to one of claims 3 and 4 wherein in at least step (iii), the acid used is a concentrated acid, preferably selected from the group formed by sulfuric acid having a concentration of at least 80% by weight, in particular at least 90% by weight, the acetic acid or the formic acid having a concentration of at least 90% by weight, the nitric acid having a concentration of at least 60% by weight, the phosphoric acid having a concentration of at least 75% by weight, the hydrochloric acid having a concentration of at least 30% by weight. 5. Process according to claim 3, characterized in that, after contacting the reaction medium with acid and silicate in step (v), an alkaline agent is added to the reaction medium obtained. preferably silicate, and this so as to increase the pH of the reaction medium to a value between 4.7 and 6.3, preferably between 5.0 and 5.8,
6- Procédé selon l'une des revendications 3 à 5, caractérisé en ce que l'acide utilisé dans au moins une des étapes (iv) et (v) est un acide concentré, de préférence choisi dans le groupe formé par l'acide sulfurique présentant une concentration d'au moins 80 % en masse, en particulier d'au moins 90 % en masse, l'acide acétique ou l'acide formique présentant une concentration d'au moins 90 % en masse, l'acide nitrique présentant une concentration d'au moins 60 % en masse, l'acide phosphorique présentant une concentration d'au moins 75 % en masse, l'acide chlorhydrique présentant une concentration d'au moins 30 % en masse. 6. Process according to one of claims 3 to 5, characterized in that the acid used in at least one of steps (iv) and (v) is a concentrated acid, preferably selected from the group formed by the acid. sulfuric acid having a concentration of at least 80% by weight, in particular at least 90% by weight, the acetic acid or the formic acid having a concentration of at least 90% by mass, the nitric acid having a concentration of at least 60% by weight, the phosphoric acid having a concentration of at least 75% by weight, the hydrochloric acid having a concentration of at least 30% by weight.
7- Procédé selon l'une des revendications 3 à 5, caractérisé en ce que l'acide utilisé dans les étapes (iv) et (v) est un acide concentré, de préférence choisi dans le groupe formé par l'acide sulfurique présentant une concentration d'au moins 80 % en masse, en particulier d'au moins 90 % en masse, l'acide acétique ou l'acide formique présentant une concentration d'au moins 90 % en masse, l'acide nitrique présentant une concentration d'au moins 60 % en masse, l'acide phosphorique présentant une concentration d'au moins 75 % en masse, l'acide chlorhydrique présentant une concentration d'au moins 30 % en masse. 7- Method according to one of claims 3 to 5, characterized in that the acid used in steps (iv) and (v) is a concentrated acid, preferably selected from the group formed by sulfuric acid having a concentration of at least 80% by weight, in particular at least 90% by weight, the acetic acid or the formic acid having a concentration of at least 90% by weight, the nitric acid having a concentration of at least 60 % by weight, the phosphoric acid having a concentration of at least 75% by weight, the hydrochloric acid having a concentration of at least 30% by weight.
8- Procédé selon l'une des revendications 3 à 7, caractérisé en ce que dans une partie de l'étape (ii) l'acide utilisé est un acide concentré, de préférence choisi dans le groupe formé par l'acide sulfurique présentant une concentration d'au moins 80 % en masse, en particulier d'au moins 90 % en masse, l'acide acétique ou l'acide formique présentant une concentration d'au moins 90 % en masse, l'acide nitrique présentant une concentration d'au moins 60 % en masse, l'acide phosphorique présentant une concentration d'au moins 75 % en masse, l'acide chlorhydrique présentant une concentration d'au moins 30 % en masse. 8- Method according to one of claims 3 to 7, characterized in that in a portion of step (ii) the acid used is a concentrated acid, preferably selected from the group formed by sulfuric acid having a concentration of at least 80% by weight, in particular at least 90% by weight, acetic acid or formic acid having a concentration of at least 90% by weight, nitric acid having a concentration of at least 60% by weight, the phosphoric acid having a concentration of at least 75% by weight, the hydrochloric acid having a concentration of at least 30% by weight.
9- Procédé selon l'une des revendications 6 et 7, caractérisé en ce que l'acide utilisé dans l'étape (ii) est un acide concentré, de préférence choisi dans le groupe formé par l'acide sulfurique présentant une concentration d'au moins 80 % en masse, en particulier d'au moins 90 % en masse, l'acide acétique ou l'acide formique présentant une concentration d'au moins 90 % en masse, l'acide nitrique présentant une concentration d'au moins 60 % en masse, l'acide phosphorique présentant une concentration d'au moins 75 % en masse, l'acide chlorhydrique présentant une concentration d'au moins 30 % en masse. 10- Procédé selon l'une des revendications 1 à 9, caractérisé en ce que ledit acide concentré est de l'acide sulfurique présentant une concentration d'au moins 80 % en masse, de préférence d'au moins 90 % en masse. 9- Method according to one of claims 6 and 7, characterized in that the acid used in step (ii) is a concentrated acid, preferably selected from the group formed by sulfuric acid having a concentration of at least 80% by weight, in particular at least 90% by weight, the acetic acid or the formic acid having a concentration of at least 90% by weight, the nitric acid having a concentration of at least 60% by weight, the phosphoric acid having a concentration of at least 75% by weight, the hydrochloric acid having a concentration of at least 30% by weight. 10- Method according to one of claims 1 to 9, characterized in that said concentrated acid is sulfuric acid having a concentration of at least 80% by weight, preferably at least 90% by weight.
1 1 - Procédé selon l'une des revendications 1 à 10, caractérisé en ce que ledit acide concentré est de l'acide sulfurique présentant une concentration comprise entre 90 et 98 % en masse. 1 1 - Process according to one of claims 1 to 10, characterized in that said concentrated acid is sulfuric acid having a concentration between 90 and 98% by weight.
12- Procédé selon l'une des revendications 1 à 1 1 , caractérisé en ce que ladite concentration en silicate (exprimée en S1O2) dudit pied de cuve initial est d'au plus 1 1 g/L. 12- Method according to one of claims 1 to 1 1, characterized in that said silicate concentration (expressed in S1O2) of said initial stock is at most 1 1 g / L.
13- Procédé selon l'une des revendications 1 à 12, caractérisé en ce que, dans l'étape (iii), on ajoute au milieu réactionnel simultanément de l'acide et une quantité du silicate de métal alcalin M telle que le rapport quantité de silice ajoutée / quantité de silice présente dans le pied de cuve initial soit compris entre 12 et 50. 14- Procédé selon l'une des revendications 1 à 13, caractérisé en ce que, pendant toute l'étape (iii), la quantité d'acide ajoutée est telle que 80 à 99 % de la quantité de M2O ajoutée soient neutralisés. 13- Method according to one of claims 1 to 12, characterized in that, in step (iii), is added to the reaction medium simultaneously acid and a amount of the alkali metal silicate M such that the ratio of amount of silica added / amount of silica present in the initial stock is between 12 and 50. 14- Method according to one of claims 1 to 13, characterized in that during the entire step (iii), the amount of acid added is such that 80 to 99% of the added amount of M 2 O is neutralized.
15- Procédé selon l'une des revendications 1 à 14, caractérisé en ce que le séchage est effectué par atomisation. 15- Method according to one of claims 1 to 14, characterized in that the drying is carried out by atomization.
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FR2984870B1 (en) 2011-12-23 2014-03-21 Rhodia Operations NEW PROCESS FOR THE PREPARATION OF PRECIPITED SILICES
JP5868520B2 (en) 2011-12-23 2016-02-24 ローディア オペレーションズ Method for producing precipitated silica
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BR112014018051A8 (en) 2017-07-11
KR20140116213A (en) 2014-10-01
EP2807117B1 (en) 2020-05-13
FR2985992A1 (en) 2013-07-26
US10011494B2 (en) 2018-07-03
FR2985992B1 (en) 2015-03-06
MX2014009002A (en) 2015-03-03
US20150266743A1 (en) 2015-09-24
CA2862475A1 (en) 2013-08-01
WO2013110658A1 (en) 2013-08-01
BR112014018051A2 (en) 2017-06-20

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